I'm a little confused why anyone would actually pay UPS and then when a bill shows up pay them again or pay them if they send a collection letter, so you end up paying them twice. If you pay UPS, you should be getting a receipt, whether you pay cash, cheque or credit card. If UPS sends you a letter saying you haven't paid, you contact them telling them you have paid. If they threaten to sue, let them. Counter-sue (because you've paid and a judge will not be sympathetic to them). They did the same thing to me, I emailed them back, said I'd paid, wouldn't pay this bill and to sue me if they'd like. I've since obtained my credit report and there is nothing on it from them and they never bothered me again. I don't ever bid on anything shipped from the US by UPS -- too much hassle!!! I guess basically what I'm saying is if you pay UPS at the door or pick it up, GET A RECEIPT!!!