You must disable "Find my iPhone" feature before you do the reset. SIM doesn't matter. A good reference for "clean" reset for the purposes of reselling/trading phones is here:
You must disable "Find my iPhone" feature before you do the reset. SIM doesn't matter. A good reference for "clean" reset for the purposes of reselling/trading phones is here:
I just followed these steps before selling my iphone X yesterday. Kept SIM card in the phone before erase and resetting. Goes without saying to back up on iTunes.