Unbelievably frustrating service

I'm on a prepaid plan.  After my month expires, I go to my account and the bill for 45 isn't there.  It just says zero balance.  When I finally got hold of a person, they pass me back to the Ai, saying they can't take my credit card number by phone.  I've had these kinds of problems many times.  They now say I'll need to find a local xfinity office to pay my bill.  What kind of outfit IS this!!!!