I believe somewhere in your contractual agreement, you must accept payments from all supported means and you cannot reject customers if they pay via credit cards. Even if they allow you to do so, you will be isolating a lot of your customer base, ie only other existing sellers who have existing funds in paypal from the 40 out of the 190 supported countries. The bulk of people who pays through paypal would do it through a credit card.
There is no way to stop CC payments,may be if u have personal account as u can accept only 5 CC payments per year to personal account.