Libsyn only lets you sign up with Paypal

Today I tried to sign up for libsyn. The system keep on defaulting to paypal when it was time to pay for the service.It seem to recognize a paypal account I used to have. I tried to use my credit card, but it wouldn't let me use it. I tried to correct the problem several times, but to know avail. This was becoming very frustrating and time consuming.