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[Q] SIM Card Crash/Unlock/Downgrading

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SoGee
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Exclamation [Q] SIM Card Crash/Unlock/Downgrading

Hi!

Apologies if repost/noob question/.

Recently I've been having issues with my phone. In the past, when using it for streaming videos and such on YouTube, my phone would start to overheat. It used to do this all the time but it was never seemed like a serious issue to me. However, for the last 2-3 weeks, whenever I used apps such as YouTube, browser, messaging etc. or anything else that might overexert the phone, it would heat up almost immediately followed by the message "no SIM card detected". I've tried rebooting the phone which occasionally fixes it (but most of the time does nothing) but the same message would pop up again within a few minutes. The only success I've had with dealing this issue is leaving the phone off for ~30min to a few hours to let it fully cool and then it would work fine again until I used an app for a prolonged period.

SO, here comes the question(s):
I've torn apart almost all the forums I could get my hands on through the glorious thing we call the internet..but to no avail. So, right off the bat, does anyone have a solution to this? I've already tried the typical 'cleaning the SIM' and 'slipping a piece of paper in with the SIM'. I've also tried the SIM on other phones (which worked fine but I wasn't able to test it to the point where it overheated as it did on mine).

TL;DR: My phone's SIM doesn't work and I need a solution.

Anyways, if noone has a solution, I have a plan of action (outlined below) but would like some advice before acting on it.

Ive tried my SIM on OTHER phones and it seemingly works fine. I HAVEN'T tried another SIM on MY phone because its not unlocked. I'm with Mobilicity and they charge $50 to unlock (given how crap their service and reception already is, I refuse to give them any more money). So, I plan on unlocking the phone myself and then test with another SIM. Sounds like alotta effort but I'm dirt poor (which is also why I'm with Mobilicity because their plans are dirt cheap) and I also find this stuff fascinating/interesting.

Research (good news)has told me I can unlock myself if my phone is on the firmware 4.1.1 (using the PersoSHA256Off method). The problem is, I'm on 4.3, which, (bad news) research has also told me, attempting any downgrade from 4.3 to 4.1.1 can result in a hardbrick. HOWEVER, (good news) I heard that this only happens if you have a locked bootloader. But (bad news), I'm totally new to android and everything I've said is simply self-educated due to research so I don't actually know how to determine if its locked (also, I get so lost in the jargon other forums use so I'm not sure I fully understand). I've heard say that Canadian S3's have unlocked bootloaders and/or come locked but can be unlocked, but again, if that's the case, how do I find out/or unlock it myself ? (I said 'lock' quite a few times, sorry if I lost anyone there).

I thank any fellow who was able to persevere through this wall of text and still has the desire to help me.
I apologize to the mods/developers/community if the answers to my questions are blatantly obvious and have fuelled anger from their hearts with its stupidity.

Here are the specs on my phone:
Model Number: SGH-T999V
Firmware: 4.3
Kernel Version: 3.0.31-2159044
Build Number: JSS15J.T999VVLUEMK5
 
DocHoliday77
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Unfortunately, there is no way back. It used to be you just hsd to flash the 4.1.1 modem, but I am not certain thatd work anymore. Up to you if you want to try, but I make no guarantees. You can buy unlock codes on eBay and elsewhere for a few bucks though.

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Quote:
Originally Posted by DocHoliday77 View Post
Unfortunately, there is no way back. It used to be you just hsd to flash the 4.1.1 modem, but I am not certain thatd work anymore.
Regardless of whether or not the bootloader is unlocked or not?
 
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The bootloader isn't locked. You just are prevented from flashing back to older firmware.

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I see. Do you (or anyone else) perhaps have a reason/solution to the main problem as to why the SIM fails after a period of time then?
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