Lost access to account

Somehow I have two account numbers one doing nothing that is somehow connected to my modem and another that I believe is charging me I accidentally unlinked the account I believe is charging me and now I have no way to stop autopay or change payment method or anything I need help to either stop the charges or get access to the account that was lost just to be clear it’s not the xfinity Id it’s the account number that I unlinked from the xfinity id