Problem: I have a phone I bought from HK and using in Japan. It has been working perfectly fine for 2 years until recently when I changed the service provider. Unfortunately, the service provider has washed its hands off the problem claiming the country of origin.

Possible Solution: I read in many forums that it could be an issue with the CSC. So I am presuming that if I can start updating the phone with Japanese OTA it might work so I intend to flash my phone with the Japanese firmware though I can't find a reference where the different firmware are claimed to be compatible.

My concern are the following:

  1. Where can I determine if the firmwares are compatible and if the worst comes to pass can I reset my phone to default factory settings?
  2. If I download a HK firmware and reset CSC to SMB (I think it is for Japan), will i actually receive OTA updates for Japan even though the firmware itself is for another location?

Question #1 Answer: http://willmyphonework.net

Question #2 Answer: Since you are looking to flash firmware that did not come on the device by default you run the risk of bricking the device. Definitely ensure if you have a bootloader that can be unlocked, and I would advise flashing twrp to begin and follow it with a full backup in case something goes wrong. You will always have the option to return to stock (make sure OEM Unlocked is ENABLED so you don't accidentally FRP Lock your device if it bricks, as this will result in a much more difficult to save situation than just a bad flash!!). As far as if your device can receive OTA updates.... typically flashing anything other than the stock firmware will result in you not being able to take OTA updates, but in the context you have asked it almost sounds as if your carrier uses a similar system to US CDMA carriers, in that it requires the "activating" or "programming" of the device to enable service. If that's the case then you just need to flash the radio.img or modem.img of the correct carrier while in TWRP recovery (only after you have backed up your current radio.img!) and then see if the phone boots and receives signal.

Second answer is a bit rough around the edges, but let me know if anything goes wrong or if you need further help and I'll be happy to help where I can.

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