Why can i not use my gift card balance to gift people things?

For christmas i sent my mum an album on itunes but it did not take the money off my gift card balance? Is it possible to do this? and if so why not?!
This is a bit of an issue for me as i didnt have any money on the account i used and i think its going to have taken it out of my account anyway leaving me in my unauthorised over draft 😟 Nightmare!!!