Database Info

SIM Card Missing (Locked?)

Ok - tearing my hair out here...
I have an AT&T Fuze I was given and am trying to get it going on Telstra NextG here in Australia.
I was fully expecting the device to be SIM locked, and am ok paying to get an unlock code, however I'm not sure exactly how to tell. When I boot the device up, it gives a missing SIM card message:
The SIM card is missing.
You can still make emergency calls if your service provider supports it.
Click to expand...
Click to collapse
...not a "Your device is locked" message. Can someone tell me what the device should look like? I'm assuming that I should get something other than a missing SIM message?
I'm starting to think that there is a physical problem with the device I have tried two Telstra SIMs, an old Prepaid Vodafone, and four Optus ones...just for good measure. (Except for the Telstra ones they aren't in service, but I assume they should still be recognise)
I've also put HardSPL and TAELROM v4.23544, and the device functions beautifully, except for no network access :-/
I've also tried putting some sticky tape on the top of one of the SIMs to try and give it a better contact, as mentioned in one of the other threads.
Yes, I'm sure I'm putting it in the right way up (SIM works fine in my Touch Pro), and all the contacts appear clean etc.
If someone else has had such an error repaired, can they tell me if it's a major task? Or fairly cheap?
Weird and the previous owner took the AT&T SIM out in front of me, and apparently it has never given any issues before.

Looks like it is sim locked to me.
at&t have an unlock.exe included in their ROM which is used for unlocking via code, you could see if your friend can get unlock code from at&t (can get free code in most circumstances! ) If he can you could flash back to a at&t ROM & unlock.
Other option would be using IMEI unlock service or olipro unlock service.

Thanks for the reply!
Ok, so this is normal? The unlock.exe doesn't fire automatically and you get a SIM missing message until you run it manually? That would be awesome if it is the case.
I could probably get a free unlock, but for the effort of calling the US I'm happy to make a donation to Olipro if that's likely to work. (And he can fix his website - opened a ticket for that)
I'm assuming the IMEI unlock service option wouldn't work unless I flash back to an AT&T ROM to get unlock.exe back, as that will just give me an unlock code which I will have nowhere to type, yeah?
Thanks again.

So, you got an AT&T Fuze (US) and you're trying to get it working on your network Telstra? Now your SIM Card, its not working on the Fuze, but it does work on your old phone? Or on any phones on your network? Any of your family/buddies SIM card work on the Fuze? Im just trying to figure out if its the SIM card or the Card reader on the device that's not working. As far as why you are getting the "SIM card missing screen" I'm not too sure about. I've searched all over the net trying to find out what kind of screen is displayed when the phone is SIM Locked, but no luck!!! Anyhow, many times these devices are locked to their specific carriers for security purposes. I did come across a few threads where people from foreign countries that bought (US) spec phones needed to SIM unlock. So i would say if money is not an issue, try SIM unlocking for a fee. Narrow down the problem. You can try this link http://forum.xda-developers.com/showthread.php?t=556059&highlight=SIM or http://raphael.sim-unlocker.com/
Two other notes:
I have an AT&T Fuze and in the (US) we have 3g networks. Before I upgraded to the Fuze my old SIM Card was not 3g compatible. It was a 2g SIM, therefore it did not work on the Fuze. (this may not be applicable to you) But note your SIM might not be 3g or the device needs to be unlocked for access to other GSM networks.
Last, my girlfriend is from Hungary and she brought a GSM cell phone, i think it was Tmobile. Anyhow I tried my AT&T Sim Card on it and the phone did recognize it...hahaha I just concluded...If the SIM Card is not recognized, then it must be missing....wow!!!
SIM Unlock, give it a shot....

Yep - AT&T (US) on Telstra (Australia).
Mister B above has given me some hope that the HW is ok, and I just need to get it unlocked... but I was hoping someone could confirm that this is normal before I spend AU$25.
All the threads I read seemed to imply that it would just pop up and ask you for a code when it detects a SIM card from a different network, but that didn't happen to me.
Also, I think I have to wait for Olipro's site to come back on the air (http://raphael.htc-unlocks.com is down for me at the moment). I'm hoping his SW doesn't required me to type an unlock code on the device itself.
Otherwise I will need to reflash the AT&T ROM back to get the unlocker.exe app (unless someone can send it to me? Not even sure where that is stored on the standard ROM to be honest.
Yeah - been through the whole 2G vs 3G SIM card before. Pretty sure my current one is good, as it's not that old and I get 3G on my Touch Pro with it.

As far as i'm aware the at&t devices do not show the unlock code window, you have to run the unlock.exe.
If you are sure the device & your network have compatable radio bands I would put it down to sim lock.
As far as i'm aware IMEI check doesn't need code input, they have support line & when I used them they were cheaper than Olipro.
http://www.imei-check.co.uk/raphael_unlock.php

Thanks (didn't realise IMEI Check was a website!)
Umm...back to nasty AT&T ROM now. Any hints where I might find unlock.exe (or a shortcut to it?)

Meh - IMEI Check website might be cheap, but they tell you AFTER you have generated the source file etc, that all first time users must validate their PayPal sale by...get this...taking photo with their camera phone of some documentation proving their identity, and email it to them...which they will process in 8 hours or so. No thanks...
Hmmm... http://www.unlocking.com/HTC-Fuze-Unlocking.html says:
"How To Enter Your HTC Fuze Unlock Code
Once you have received your HTC Fuze unlocking code, it is very simple to enter it:
- Insert any Sim card into the handset
- Turn the phone on
- You will be prompted to enter and Unlock Code
- Enter the code we provided
- Your phone is unlocked"
Double Meh. That's the bit I'm having issues with...

Ok. Used sim-unlocker.com, and once the software had finished doing it's thing, it popped up a box on the phone asking me to input the code.
Trouble is, SIM still not recognised Guess I'm looking at a fraked phone... (What a waste of time and money that was)

That is a bummer, you saw it working with the at&t sim, yes !
The fuze supports the 850MHz UTMS band so it should work fine on next G.
You could try flashing a generic HTC ROM complete with radio & seeing if you get any luck with that.
Also try some more packing on the sim card just in case it is simply a contact issue.
Total bummer if the fuze has developed a fault.

Thanks for everyone's help. It's in getting a quote for repair. Looks like I stuffed one of the pins when I put the SIM card in for the very first time :/

you gotta go to comm manager and start gsm or phone service then it'll say your phone is locked and ask for an code

Zilch said:
Thanks for everyone's help. It's in getting a quote for repair. Looks like I stuffed one of the pins when I put the SIM card in for the very first time :/
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Click to collapse
What are the odds on doing that, total bad luck.

HTC Fuze is lock to AT&T
djteotancolis said:
you gotta go to comm manager and start gsm or phone service then it'll say your phone is locked and ask for an code
Click to expand...
Click to collapse
The only way is use the simunlocker software ore buy it for $2.70 US dollar on ebay to get the unlock code from the guy name blowfish06 or get the code from AT&T. I unlock over some of them. It will automatic trigger the promt for unlock code if you put any sim that is not from AT&T in the phone.

Just as an update...
SIM slot contacts were stuffed. $150 to fix at the local repair shop in the mall. All working and unlocked now.
A SIM from a different network should pop up a message, but wasn't due to the HW fault. The unlocker software popped up this message when it was run however, so I was able to unlock it while the SIM slot was stuffed.
Thanks for everyones help.

Zilch said:
Just as an update...
SIM slot contacts were stuffed. $150 to fix at the local repair shop in the mall. All working and unlocked now.
A SIM from a different network should pop up a message, but wasn't due to the HW fault. The unlocker software popped up this message when it was run however, so I was able to unlock it while the SIM slot was stuffed.
Thanks for everyones help.
Click to expand...
Click to collapse
You could have just replace the hold sim stray just for $17 on ebay.

Yeah most likely. But I was a) lazy, b) in a hurry and c) it was a work phone so I claimed it

A different sim unlock question.

I have a T-Mobile sensation,S-off, xboarders CM7 rom... located in AZ. I do not have another sim card for another carrier, I obtained the unlock code from the terminal emulator method. I "THOUGHT" unlocking the sim card was enabling my current sim card/sensation for t-mobile, to work on other carriers.
However I obviously learned that the only way to enter the code was to insert a sim card from a different carrier, and enter the code. That being said, if I insert another sim card in my phone "like a friend with AT&T", will it affect his sim card at all? And when I put my sim card back in, will I be able to use different networks? Will it lock my sim card out of my phone or vise versa? I have been researching for a while now and I havent found too much defining what im looking for. Any one who can enlighten me would be appreciated!

all unlocking your phone does, is allows it to use different sim cards to run on different networks.
your available networks are controlled by your sim card, and any unlocking won't change that. No it won't effect your friend's att sim card, and not it won't hcange anything currently. However, if you were to get a different carrier that uses sim cards, then you could freely insert that sim card and then use their network with their sim card, provided you have the available frequencies supported (i.e. 3g/4g).

That makes sense. So people who have their phones sim unlocked usually sell the phone or have another sim card for a different network, which means they pay for two data plans? Well I feel like I wasted my time, I sure am glad I didnt pay to get my unlock code. On the bright side, the research I did find mentioned a higher resale value for the phone. However I dont see myself selling my sensation ANYTIME soon !
I appreciate the input, and thank you for your time sir!

ibmaxin said:
That makes sense. So people who have their phones sim unlocked usually sell the phone or have another sim card for a different network, which means they pay for two data plans? Well I feel like I wasted my time, I sure am glad I didnt pay to get my unlock code. On the bright side, the research I did find mentioned a higher resale value for the phone. However I dont see myself selling my sensation ANYTIME soon !
I appreciate the input, and thank you for your time sir!
Click to expand...
Click to collapse
Its a wasted of time when you are on a contract and do not planned to sell the phone, but if you travel inside or outside the country is a DAMN good advantage cus you just change or get a local SIM and you dont need to buy a new phone.. you see?
And also like you said "higher resale value for the phone"

myTouch 4G Slide sim unlocking

Here we go with yet another unlock solution.
This one applies to almost (if not all) devices which are radio S-off, it’s fairly easy to use and doesn’t wipe data/settings nor have that ugly side effect (when using diag files) in which you lose conectivity to mobile network.
Supported devices so far:
HTC Sensation (pyramid)
HTC Evo 3D (shooter)
HTC EVO 3D GSM (shooteru)
HTC myTouch Slide 4G
Click to expand...
Click to collapse
(by the use of revolutionary)
and:
Sprint EVO 4G
Droid Incredible (HTC Incredible)
HTC Desire CDMA (HTC BravoC)
Click to expand...
Click to collapse
(by the use of unrevoked 3 – not tested)
These are the required steps you have to take:
1. S-off your phone by using Revolutionary (if you haven’t already done that).
2. Fill in the form with the required data. This will generate an unique Config.dat file for your device. Please enter a valid email address, as you’ll be sent there the link to download the file.
This step you'll have to take here
3. Put the file on the root of your sdcard and reboot your phone into HBOOT (adb reboot oem-42). Once you’re there, navigate to Simlock and press Power. The phone will load the file and remove the simlock. Some text will appear on the screen and at a certain point you’ll be asked to press Vol-Up to restart the phone.
4. Just do it, and you’ll be done!
PLEASE NOTE!:
This solution is heavily linked to the device it's being applied to by the use of IMEI, which can be considered a breach in security.
DISCLAIMER:
This solution provided for you on this site is given AS IS and in GOOD FAITH and is based on the research I made. I may not accept any liability or responsibility for the use of this applicaton.
If you find this tool useful and appreciate my work, Paypal me a beer, it helps development a lot..
​

This really should be in the development section.
Sent from my myTouch_4G_Slide using xda premium

if you just need a SIM unlock, call T-Mobile and they will give you an unlock code. there is no need to fuss around with complex steps.

Climbguy said:
if you just need a SIM unlock, call T-Mobile and they will give you an unlock code. there is no need to fuss around with complex steps.
Click to expand...
Click to collapse
Not for certain circumstances.. T-Mobile will only give it you you if you meet some criteria.. i.e. you're account has been active for 6 months.. I don't know what the actual criteria are.. that was just an example...
not to mention that you have to wait over 24hours to get the email with the unlock code.. this method was a lot faster than a half hour phone call with a t-mobile rep.

I was a customer for about 6 days and was given the code over the phone.
michaelmab88 said:
Not for certain circumstances.. T-Mobile will only give it you you if you meet some criteria.. i.e. you're account has been active for 6 months.. I don't know what the actual criteria are.. that was just an example...
not to mention that you have to wait over 24hours to get the email with the unlock code.. this method was a lot faster than a half hour phone call with a t-mobile rep.
Click to expand...
Click to collapse

Climbguy said:
I was a customer for about 6 days and was given the code over the phone.
Click to expand...
Click to collapse
And I'm not, never have been, and never will be... a tmobile customer....

Just unlocked my friend's MT4GS and it works great with her prepaid running on AT&T's network! This method works great.

Link in my sig has another way using terminal emulator. Ill add this to the compendium
sent from my sense on crack MT4G Slide using xda premium

Silly question but, this method will not work on a mytouch 3g slide right? I mean can revolutionary sim unlock a mt3g?

enelyam said:
Silly question but, this method will not work on a mytouch 3g slide right? I mean can revolutionary sim unlock a mt3g?
Click to expand...
Click to collapse
Rev is used to gain s off that's all. Which allows unsigned flashing
As for the unlock methods you may want to test this out my sig has this method and one using terminal emulator method no idea if they will work.
sent from my sense on crack MT4G Slide using xda premium

Droidmoder said:
Rev is used to gain s off that's all. Which allows unsigned flashing
As for the unlock methods you may want to test this out my sig has this method and one using terminal emulator method no idea if they will work.
sent from my sense on crack MT4G Slide using xda premium
Click to expand...
Click to collapse
I know this thread is WAAAAY old, but wanted to let people know this still works.
I went to this link: http://forum.xda-developers.com/showthread.php?t=1801106
And followed the instructions to achieve S-OFF on a stock ROM. Then followed the instructions from the post.
For returning to stock, I just had to google the filename to find a working mirror, as those provided in the articles don't seem to be working. Thanks OP!

my touch 4g Slide NO CALLS with S-off sim unlocked METROpCS
So its 2014.. I know I should get a better phone.. Good news its I got my my touch 4g slide bootloader unlocked and S-off. Also did the sim unlock on the site that emails you back the file and unlocks the sim.. BUT here is my problem
when I put my metro sim in the phone.. no matter which rom I load (which I can now load rom recovery from sd) the phone wont work..
When I go into the settings metropcs and att show up but when I try and select it, it tells me not allowed right now, or sim card doesn't allow that connection. So I cannot get it to work. Is there a way they are locking sim cards to their phones?
I would have thought getting S-off and running the simlock file I'd be good to go.. Anyone PLZ help I am desparate to figure out what is wrong here.

Picture Of S-off UNLOCKED bootloader NO SVC
Here is a picture of the phone.. Likewise no SVC with metro sim.. I don't have a tmobile card to test with but I think either the sim lock didn't work, or metropcs is somehow locking the sim to IMEI
Anyone with ideas here plz help. If it is IMEI to sim is there a way to unlock sim or change iMEI? I know its illegal to change an ESN but imei..
Also if its blacklisted would it be blacklisted for metro too?
i57.tinypic.com/2my6a6g.jpg add the http part

Simbalage22 said:
Here is a picture of the phone.. Likewise no SVC with metro sim.. I don't have a tmobile card to test with but I think either the sim lock didn't work, or metropcs is somehow locking the sim to IMEI
Anyone with ideas here plz help. If it is IMEI to sim is there a way to unlock sim or change iMEI? I know its illegal to change an ESN but imei..
Also if its blacklisted would it be blacklisted for metro too?
i57.tinypic.com/2my6a6g.jpg add the http part
Click to expand...
Click to collapse
So I thought of a couple things. With a little research, one got shot down right off the bat:
http://www.phonescoop.com/carriers/carrier.php?c=11
http://www.gsmarena.com/t_mobile_mytouch_4g_slide-4018.php
Some carriers use weird frequency bands that the phone wouldn't support. MetroPCS uses 1700 or 1900MHz (depending where you are), which the phone totally covers. So not that.
Related to that though, is the APN settings. If you have more than one (my Rogers setup has 4), it may be stuck on an APN that just isn't working for you. So Settings > Mobile Networks > Access Point Names.
Finally (just thought of it), you may want to test your MetroPCS SIM card on a different (smart)phone. I had recent problems with my SIM (I guess it was swapped out too many times, besides being 6-7 years old), although it worked fine on a feature phone. And if you can get your hands on a different SIM (T-Mobile or otherwise), and encounter the same problem, it could very well be a (hard-to-resolve) problem with the phone. If it is blacklisted, it would be blacklisted nationally if not internationally, and there is an IMEI database to check it against:
http://www.imei.info/
Hope this helps.

Check your imei for blacklist status on the tmo website. MetroPCS is now wholly owned by TMo, it shouldn't need to be unlocked. AT&T and Tmo share blacklist data as well. If your phone is sketchy you are out of luck.
If the SIM is old you might try a new one and see if that helps.
Hastily spouted for your befuddlement

MetroPCS marries SIM to IMEI
Coug76 said:
Check your imei for blacklist status on the tmo website. MetroPCS is now wholly owned by TMo, it shouldn't need to be unlocked. AT&T and Tmo share blacklist data as well. If your phone is sketchy you are out of luck.
If the SIM is old you might try a new one and see if that helps.
Hastily spouted for your befuddlement
Click to expand...
Click to collapse
ok So my cousin has a metro. Tried her sim,same results. So I said hmmm. Stuck her metro sim in my metrophone and vice versa. Same result.. So I I am thinking witgh 4g unlimited they are locking the sims. Called and wa told they marry the sim to the imeI. LOOKS like the days of swapping sims to different phones are over. Anyone know a way around this PLZ let me know. ALSO tethering would be cool but i'll google that.. comes as an FYI

Simbalage22 said:
ok So my cousin has a metro. Tried her sim,same results. So I said hmmm. Stuck her metro sim in my metrophone and vice versa. Same result.. So I I am thinking witgh 4g unlimited they are locking the sims. Called and wa told they marry the sim to the imeI. LOOKS like the days of swapping sims to different phones are over. Anyone know a way around this PLZ let me know. ALSO tethering would be cool but i'll google that.. comes as an FYI
Click to expand...
Click to collapse
I was looking into this, and this forum thread came up:
http://www.howardforums.com/showthr...-married-to-ESN-of-one-phone-only-that-sucks!
Looks like you can transfer phones by letting MetroPCS know of the new IMEI, but you cannot register two (or more) IMEI's for the same SIM. So depends on how you want to use your Doubleshot. I'd give them a call (or better yet, go into their store), maybe the old IMEI will still work (the thread was a bit iffy on this result) with the new (Doubleshot) one entered.

Thanks
joel.maxuel said:
I was looking into this, and this forum thread came up:
Looks like you can transfer phones by letting MetroPCS know of the new IMEI, but you cannot register two (or more) IMEI's for the same SIM. So depends on how you want to use your Doubleshot. I'd give them a call (or better yet, go into their store), maybe the old IMEI will still work (the thread was a bit iffy on this result) with the new (Doubleshot) one entered.
Click to expand...
Click to collapse
Wow! so that's a bummer. I really like the doubleshots keyboard but I think the exhibit from them is better. Although I tried several firmwares on it and Netflix will no longer work with custom roms (thank DRM for that) I did get hella mods to this one, but would love to have both, I was thinking the sim was somehow locked. I have a sim reader any software to check? copy clone??? new to GSM, but know lots about CDMA.. I wish it were easy to just clone IMEI like ESNS

Issues Unlocking Infuse

Just bought a used Infuse, already have it rooted and running Paranoid Android Jellybean, but I'm having trouble unlocking it. All of my other phones were unlocked automatically when I flashed a custom ROM, but this doesn't seem to be the case for the Infuse. The phone won't detect my T-Mobile SIM at all, even to say "Invalid SIM" etc. Now, I know one of the first suggestions will be "reflash" but at this point I've tried 2 custom ICS ROMs, unofficial CM9, Zeus, and have flashed PA 3 times, and none of them are detecting my SIM or prompting me for the unlock code, which I've already obtained. Is there any way to force the prompt for unlock code, or some other way to enter the code, some way to do it through Odin, or using the PC...just looking for any way I can get it unlocked.

http://forum.xda-developers.com/showthread.php?t=1176886

Gilligan87 said:
All of my other phones were unlocked automatically when I flashed a custom ROM, but this doesn't seem to be the case for the Infuse.
Click to expand...
Click to collapse
That's news to me. I don't think I've ever flashed a ROM that automatically SIM unlocked the phone as well.
It seems very odd that it wouldn't prompt you for the unlock code as soon as you put a foreign SIM card in it. Have you tried an actual AT&T SIM card in it just to make sure that there's not a hardware issue with the SIM card reader? Also, it may be worth going all the way back to stock and seeing if it gives the prompt.

Pony Express said:
http://forum.xda-developers.com/showthread.php?t=1176886
Click to expand...
Click to collapse
Like I said, I already have the unlock code. I just can't get the phone to prompt me for it. I read that thread, it's actually the one I used to obtain the code, and didn't see anything that helped with my particular dilemma.

Gilligan87 said:
Like I said, I already have the unlock code. I just can't get the phone to prompt me for it. I read that thread, it's actually the one I used to obtain the code, and didn't see anything that helped with my particular dilemma.
Click to expand...
Click to collapse
I'm on the latest PA build and I was able to unlock just fine. Is it reading an AT&T sim card? First off make sure that the sim card you are using is actually activated. I just got a straight talk sim card that has not been activated and when put into my phone I was not prompted for the unlock code. I used my sister's T-Mobile sim card and it prompted for it. Make sure you swap them while the phone is powered off as well.
Sent from my SGH-I997 using xda app-developers app

mrhaddan said:
I just got a straight talk sim card that has not been activated and when put into my phone I was not prompted for the unlock code.
Click to expand...
Click to collapse
Unless you bought Straight Talk's T-Mobile BYOP SIM card, you wouldn't be prompted for an unlock code. Straight Talk's AT&T based SIM cards will work right off the bat, with an AT&T branded phone. When I used the hex editor method to find my unlock code, I used an old T-Mo SIM card that hadn't been active for well over a year, and I was prompted for the code as soon as I booted the phone up.

ApexPredatorBoids said:
Unless you bought Straight Talk's T-Mobile BYOP SIM card, you wouldn't be prompted for an unlock code. Straight Talk's AT&T based SIM cards will work right off the bat, with an AT&T branded phone. When I used the hex editor method to find my unlock code, I used an old T-Mo SIM card that hadn't been active for well over a year, and I was prompted for the code as soon as I booted the phone up.
Click to expand...
Click to collapse
It is an at&t compatible sim card, so maybe that is why it didn't prompt, I just thought it was because it wasn't activated.
Sent from my SGH-I997 using xda app-developers app

Still baffled on this, if anyone knows how to force the unlock request screen, or some other way to unlock the phone, I would be very appreciative. Will donate for proper answer.

Gilligan87 said:
Still baffled on this, if anyone knows how to force the unlock request screen, or some other way to unlock the phone, I would be very appreciative. Will donate for proper answer.
Click to expand...
Click to collapse
Go to a T-Mobile store and pick up a prepaid SIM with 10 miniutes of air time. Power down your phone, and insert the SIM card. Power back on your phone, and you should be prompted for an unlock code. Your phone will be permenantly unlocked after entering the code and pressing enter.

k-semler said:
Go to a T-Mobile store and pick up a prepaid SIM with 10 miniutes of air time. Power down your phone, and insert the SIM card. Power back on your phone, and you should be prompted for an unlock code. Your phone will be permenantly unlocked after entering the code and pressing enter.
Click to expand...
Click to collapse
Thanks but as I've said I've already tried the standard method.
It seems most likely that its a hardware issue; the phone isn't even reading AT&T Sims, so it might be a lost cause at this point.

How to enter unlock code

I have a s-off, boot loader unlocked, rooted AT&T HTC One X. I got an unlock code and have had it for some time because I wanted to use the phone on Straight Talk. I ordered a Micro SIM card from the straight talk website and inserted it and booted up the phone and all it says is Unprovisioned SIM Card. I have tried flashing different stock roms, and the current one is a stock rooted rom. All the tutorials I've seen say that when it boots up it should request a cell unlock code on screen, but mine doesn't.

SebringTech said:
I have a s-off, boot loader unlocked, rooted AT&T HTC One X. I got an unlock code and have had it for some time because I wanted to use the phone on Straight Talk. I ordered a Micro SIM card from the straight talk website and inserted it and booted up the phone and all it says is Unprovisioned SIM Card. I have tried flashing different stock roms, and the current one is a stock rooted rom. All the tutorials I've seen say that when it boots up it should request a cell unlock code on screen, but mine doesn't.
Click to expand...
Click to collapse
Provisioning a SIM card is sort of programming tariffs, features and functions to it. That is something your operator does before they give you a SIM card (usually it is done way in advance at the factory). In the modern world, however, operators may opt for SIM cards that are not programmed beforehand, but for such that provisioning process will happen the first time you put it in the phone. I'm am not sure if this must be an interactive process to the user, but the SIM card sure needs to communicate to the mobile network. I would imagine that in a SIM-locked phone it just can't talk to its home network to get initialized the way it needs to.
Please take everything I said with a grain of salt - I have but a very vague picture of the process and may be making stuff up, but as someone that has just recently unlocked their SIM-locked AT&T device, I can assure you that with good old normal SIM card from years ago (that I have) the device asks for an unlock code like all tutorials say it does.

You need to be in stock rom or be not root
Sent from my Nexus 4 using xda app-developers app