fraud - added payment to business account that's not ours

We have a bulk business TV account for our senior community. When a resident added services somehow Comcast began applying our business account and our payment to their credit card. We do not see the card online on our accounts to remove it. Calling comcast has been more than difficult and they indicate they can't see the card either so the elderly person must file a fraud claim. however, no one seems to be able to give me the right number and we get disconnected from the regular fraud department when being transferred to business fraud. This person (whom we tracked down the card for by literally calling and asking as we see the card type and last four digits of the payment method provided in an automatic payment confirmation email only) we are told is the one who needs to file a claim but the form doesn't make sense - there's no identity theft, there's no stolen/missing card, etc. it is Comcast who is applying payment and yet they say they do not see the card to remove it either or they are not authorized. Can someone please tell me how we assist this elder in our senior living community file a claim so they stop charging his credit card for an account he doesn't even have access to? What number do we call, what form do we file??????