In the Netherlands a "credit card" is referred to as "credit card" and not creditkaart or kreditkaart. By the way, credit is the correct spelling and not kredit.
In Belgium the term kredietkaart (please note the second "e" in krediet as opposed to kredit) is frequently used for a credit card. So, to have a useful domain name you should register kredietkaart.be if it is still available.
I just checked for you. KredietKaart.be is already registered.