I've bought this phone second hand and its locked to Xfinity Mobile and would like to use the phone on a different carrier. Could I unlock this?
I have no information on the original owner.
You are likely to have a difficult time unlocking a phone where you don't have contact with the previous owner. The carrier is probably going to want the account holder/previous owner to request the unlock. If you succeed in unlocking it, you might then find that it is blacklisted.