Trying to make an iTunes purchase, keep getting "Verification Required" message how do I fix this?

I am using my iPhone and trying to purchase a season of a TV show on iTunes. I have $10.00 credit on and wanted the remaining balance to be charged to my debit card connected with my account. But every time I press "Buy" I keep getting a message that says "Verification Required" so I press continue and it takes me into my settings > Manage Payments to verify my information. It keeps asking me to enter the CVV code on my debit card. I enter the the number, press done, and then it takes me back to the iTunes store. I press "Buy" again, and the cycle starts all over, again taking me back to settings to verify my payment information and asking me for my CVV code number all over again. It is apparently not saving when I enter it. I then went onto the Apple website, signed into my account and tried to edit my payment information from there, and the same thing happened it was not saving my info. I even tried restarting my phone and that did nothing. Is there a solution to this problem?