do i need sim card to erase iphone

Trying to wipe my old iphone. New phone is working. The sim card is in the new phone. When erasing old phone i get screen asking to turn off "Find My" and activation lock. It wants apple id and pwd. The phone doesn't have network access, SOS showing up in network icon. After i enter the pwd, it comes back with Verification Failed message. I can never get past this screen to began deleting data. Does the phone, need to have network access to turn off the "Find My" and activation lock? If i put the sim card back in will it mess up the new working phone?