purchase could not be completed message keep popping up each time i try to purchase something with my appstore

If you are also getting a message to contact iTunes Support you should contact iTunes Support (these are user forums, not iTunes Support) :

- go to http://www.apple.com/support/itunes/ww

- click on your country's flag (the country where you live, and which is therefore the country on your account)

- click on Contact Support towards the top right

- click on Get Help under 'Talk To Us'