Final bill and balance confirmation for closed/inactive account

I canceled my Xfinity service and returned my modem. However, I recently received a text message saying that a bill is due, but I cannot verify whether I owe anything.

When I log in, my account shows a balance of $0.00, but the billing history displays my previous service address. My most recent service address is listed as the primary and default address in my account settings, but that service is marked as inactive, and I cannot access its billing history or final statement.

The online chat keeps directing me to call customer service. However, I am currently permanently outside the US and cannot call the US support number.

How can I contact a live assistant so I can check the final balance associated with my most recent service address and confirm whether I owe anything?

Thank you.