I want to map my domain with wordpress but i have a problem

I purchased a domain form bigrock..i want to map it with word press..i have to pay 12$ for it .. the problem is when i am trying to purchase it asking for credit card. but i don’t have credit card.. i have a debit card
but it is not working.. in paypal there have same problem..i want to purchase it. is there any option by which i can buy wordpress mapping without credit card..