I both agree and disagree with your complaint. I disagree because I have had a Care Credit card for at least two years, and a Car Care One card for over a year. I have taken advantage of several "x months no interest" promotions, and never had a bit of trouble with payment posting. I have conducted all my business regarding these two accounts online.
However, I agree because my PayPal Mastercard has given me nothing but grief. First of all, they have these ridiculous rules regarding online payment scheduling. You cannot schedule more than one payment a day, and you cannot make more than two online payments per billing cycle. I can understand a company wanting to curtail people making numerous small payments, but no other credit card I have has rules like this. Secondly, a month or two ago I did a balance transfer of three cards (including PPMC) to a different card with no interest. Two of the three cards posted the payments within 48 hours and gave me immediate access to my credit line again. PPMC, on the other hand, had not posted the payment after more than two weeks. When I finally called to complain, I was told that it was standard procedure with large payments. I told her I could understand that if I'd written a personal check, but they received an electronic funds transfer from a nationwide bank. There was no excuse for them to freeze it, and I had no such issues with my other transfers, one of which was even larger than PP. I've made a few more small charges to the card, but as soon as I pay it off I will be closing it.
