Xiaomi 13

@syaoran hi can you expand upon what an implementation of VoLTE is and why it isn't universal? I have a redmi note 13 pro + (CN ROM) that worked for a few months before suddenly getting signal cut off (no calls or data).

I couldn't recall whether it coincided with the hyperOS update but I've read some horror stories on forums blaming the update for loss of cellular connectivity. I even paid xiaomi service to downgrade my OS back to miui to see if that would resolve the issue - didn't work.

I was using mint Mobile which works off of tmobile's network, and mint mobile's IMEI checker claims the phone was incompatible even though it worked for a few months, whereas tmobile's IMEI checker confirms my phone is compatible?? Does IMEI compatibility also imply certification or..? Idk if xiaomi phones are even certifiable in the US, but some forums claim their 'uncertified' phones are somehow working...?

I don't know if it was one of your previous answers or some other forum I read where they said flashing a different rom won't change the connectivity settings (I'd have to repay xiaomi service to unlock my bootloader anyways 😒) but is that true? Could my issue really be a hardware problem, or a firmware/software problem? I added a picture of bands compatible according to kimovil for ref. I read one of your comments on another post where you mentioned using 'qpst', is that something that lets you configure the firmware responsible for cellular connectivity or unlocking bands or something...? Is there a mediatek version of that?