This user, mountaingoatgirl, explains how to get a None (No bank card) option in your account details in the iTunes app on a Mac or PC. -
https://discussions.apple.com/message/24907941
Late 2012 Mac mini, OS X Yosemite 10.10.5; Apple Watch, 38 mm silver AL, watchOS 1.0.1; iPad Air 2 & iPhone 6+, iOS 8.4.1