Cannot access Xfinity ID for new service

I have an old xfinity login account that is my mother’s from her old address and it’s inactive. When i first signed up for new service since im moving into a new place on tuesday, it said my phone number was already associated with an account (my moms old one) i went in and changed the phone number on her old account so i can use my phone number for my new account. It keeps saying “this information doesn’t match our records” and will not let me sign in or reset anything to matter if i use a phone number, email address or username. 

Please help, i need this figured out before i move in