What software is used to flash my iphone to cricket from tmobile?

[iMore Question]

So I purchased an iPhone 6s for tmobile on offerup. When I met with them I put my sim card in and the phone was activated and worked with no issues. 3 months later all of a sudden my service is no longer working. Called tmobile and they couldn't tell me much except that the phone can no longer work. So I know I'm out of luck on tmobile but I'm hoping to flash the phone and switch to cricket. I know they can flash it but I don't really want to lose out on more money. I've searched but can not find any reliable software to flash my phone.

If anyone know anything software that would be great

Thank you for your time. and promise the phone isn't stolen. I can show anyone the messages on offer up from when I bought it.

 

[Deanig_12]

why dont you just get it unlocked? that way u can put any sim in

 

[pkcable]

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Ok not everything is adding up in my mind. Why did it stop working suddenly? Did the previous owner report the phone lost or stolen to T-Mobile OR leave an unpaid balance? Usually T-Mobile will go out of their way to resolve problems with signal, such as sending you a signal booster, informing you about repair work to towers in your area, etc. I'm just not getting the "out of luck" with T-Mobile comment. It really sounds like the previous owner skipped out owing. You MIGHT want to contact them and request a refund. On the iMore Market Place, Swappa, or Ebay, this type of seller would most likely be banned.

I don't think anyone is going to be able to help you if this turns out to be a device locked due to a default on a carrier loan, or something along those lines.