Some of website are accepting credit card but they want some documents or proof that you are really the holder of that card because they're implenting rules againts fraud because of dispute transaction or malicious activity that hackers do when they hacked credit card but if you have any other payment method like paypal you can exchange it to bitcoin easily go to exchange currency thread
Definitely avoid those credit card sites. Even if they are legit, the fees are so high you might as well not buy any in the first place.