Error message: "Failed to bill youur account"

Hello! I really need some help here, if anyone can help me with it I apreciate it very much. Here's the problem:

I want to buy Lindens with my DEBIT CARD, VISA. I'm from Romania and yes, i have enough money on it and yes, manyyyyy days have passed since i filled my bank account. The problem is that on LindeX (linden exchange) the system doesn't let me to. It accepts my card information but it won't bill it. The error message is: "Couldn't purchase currency.Failed to bill your account. Please double check ur account's payment settings." The same error is in the game when i click on the Lindens Dollar sign to exchange money.

1)why doesn't it bill my card?
2)must it be a CREDIT card? i only have a DEBIT one.
3)if the error keeps appearing, what other sites do u know where i can buy lindens from ? SITES DON'T USE PAYPAL, cause Romania doesn't have paypal

Thank you very much friends

AngeyLaura Houston