How do I retrieve my 16 digit account number?just moved and received a new modem from you and have been on auto pay for several years.

Need help retrieving my full account number. I moved into a new home and set the transfer of service for Saturday. Well the new modem arrived yesterday. I tried calling to activate service and can’t get by the automated system. It recognizes that I have new equipment but directs me to the Xfinity app. No other options. I’m unable to sign on after resetting my password and just not being recognized. Online chat last night can’t proceed without my full account. I have the last four of my acct. I found that on the order confirmation. They’re telling me that I’m using the wrong id but can’t get it without my full account number. Help!! Ron [Edited: "Personal Information"]