iTunes wont Authorise my Computer

When I type in my password, a message pops up saying 'The requested source was not found' and I have an 8GB iPhone 5c so I need it to connect so I can remove music ect.

Also when I enter my billing details, it pops up saying invalid billing details when it's not and I retyped it about 5 times (both w/ spaces and w/out)

Can anyone help? 😠😟