Most of credit card processors that adult industry uses are flagged as high risk and suspicious, regrettably. CCbill may be the only exception because it was here more than 15 years and quite big.

And "clean" processors simply would not deal with adult sites.

Also, some small banks block all overseas transactions by default. I don't know which is your case.

So, as Ray said, you would probably be better with a prepaid card. It's better to use online anyway, more secure - even if the number gets stolen, it's not connected to your accounts.

Check with your bank in person, I had the same problem a few years ago with another site,come to find out some banks will not honor payments to X rated sites and Dating sites.
To remedy the problem I suggest you get one of those pre paid cards (from Walmart for example)and do your payment through there