Xfinity Support-Just moved addresses and need to pay final bill at old address but cannot find the old bill anymore

Hello- I just moved and I need to pay my final bill at my old address. Yet, when I log into my xfinity account it is not letting me switch accounts to my old address and my old address account number is no longer showing up under my new xfinity account. I got the email to do it but the links on the email all bring me to my current account showing a $0 balance with no way to find my old one. Please help.