Juhi,
If you're doing this as a student as you claim to be, you really don't want to be handling real credit card numbers. It's a huge security risk for users and there's really no reason you need to use real ones. Instead, create your own imaginary credit card numbers and your own validation scheme. To answer your question completely, the only folks who will legally validate credit card numbers are the banks and the credit card companies who have direct access to the credit card infrastructure. If just anybody could validate a credit card number, it would be relatively easy for any script kiddie (you're not a script kiddie, are you, Juhi?) to brute-force some credit card numbers and go on a shopping spree.
