I recently replaced my iPhone. A friend tried to erase the old phone to use it for himself but was told it still had a live bank account - I assume my bitcoin account. How can I retrieve my account and bitcoin? I still have my old phone but not much else - anything I can do?
A bitcoin app would not stop your phone from being formatted, so it must be something else.
That said, if you still have bitcoin in a wallet on your old phone, then you should definitely transfer it to a wallet on your new phone (or maybe just recreate your old wallet on your new phone). Just open up the bitcoin wallet, and transfer the funds / export the seed phrase.
Retrieving the bitcoin won't fix your problem of being unable to format the phone, but you should definitely not sell your phone until you have done so!