Unable to add funds to PSnetwork? *help*

So I want to download some games and such but when i put my card info in it tells me ''invalid'' or something even though everything is exact. I am trying to use a debit card but will it only work with actual credit cards? If so is it true that those PSN redeemable cards are hard to find?ThanksUnable to add funds to PSnetwork? *help*
If it's a prepaid debit card, it won't work. If it's a debit card associated with a checking account, then I don't see why it won't work.