Basically, you can't easily buy hard money (like Bitcoins) with soft money (like credit card payments). The problem is that customers could reverse or dispute the soft money payment and the trader couldn't get the hard money back. To cover their costs should this happen, they'd have to give lousy exchange rates.

These lousy exchange rates would chase away legitimate customers. But scammers wouldn't mind, they're not going to pay anything anyway. So the scam rate goes up, the fraud losses go up, the legitimate customers get chased away, and so on.

There do exist businesses doing this, but expect extensive credit checks, waiting periods, demands for detailed documents, and so on. Also, expect to pay too much.