How to Download Psp Games for Psp Go from Playstation Store?

I bought PSP GO n i bought it from Dubai,n i created a account in platstation network by chossing country/region as UAE n i try to buy game from playstation store using credit card n i gave all information which is necessary,it says"credit card information is not valid".Pls help!

Suggestion:

If your using a VISA card try a master card and viceversa