Can them up and say you want to transfer the membership to another account or call them and cancel the membership and see if they can reimburst you with a code for more gold
Last time I did it, I called them and said I wanted my rank reset on Black Ops and they said the only thing they could do is remove the gold from my account and they would send me the code(s) to my email and then I got it.
Quad has a private method if you want to put the gold on another account, Xbox support doesn't allow you to unless you're just putting it back on where you took it off from.