Unable to create Xfinity ID with old phone or email

I recently moved to a new address and transfered service. I haven't gotten the account number for my new address, and I tried going to the page to Create an Xfinity ID. But it asks to provide a contact method to get started, and both the email address and phone number I try to provide don't work because they're already in use by my existing account. How do I get my new account number with my existing email or phone number?

Also, there seem to be a few issues in billing. It says on the main account page that my bill was due earlier, but I know I scheduled a payment for the day before. I can't seem to find a way to check if it's been paid, and when I go to billing it shows that I have a total balance due that's much less than the original bill, but has the same due date if I try to go pay it. I want to talk to a representative to resolve these billing issues.