I can’t pay remaining balance on closed account

I have moved and do not have any mail related to my account. I do not have account number and I was never able to link it to my active account for another service address (despite being told I had successfully done so). I was also told when I closed the account that there was no outstanding balance. I was also told when called the first time about a device that should have been returned, even though it was supposed to be linked to my active account, that the account I’m inquiring about was all set, closed, no further actions needed. So I’m curious now why I am unable to access in order to pay this magical balance that multiple individuals that work at Xfinity were apparently unable to see and why I was never able to create an account to begin with.