i cant complete my billing information

i created an apple ID with my Gmail acc. i tried to download an app, it asked me to review and then i had to put my billing information. I put all the information but when i click next i get this: FOR ASSISTANCE CONTACT ITUNES SUPPORT AT WWW.APPLE.COM/SUPPORT/ITUNES/WW/.

I tried this site but i couldnt figure out what the problem is.