A new iPhone and wrong Apple ID credentials

We bought a new iPhone, created an Apple ID & set up iCloud. Now there is a game on the iPhone that needs an update. So when we try to update that game it has a completely different Apple ID and phone number from what we set up the new phone with. We can't change the password because the phone number doesn't exist. We are looking for suggestions on how we might be able to fix this. I have already erased the phone and started over but that still comes back to update.