OK, i've turned autorenew OFF but it didn't let me delete my card as said 'there is an outstanding balance on this payment option, try later' which there isn't....
Also i'm disgusted autorenew was on anyway. As far as i knew i bought a 1 month subscription to XBL, why on earth does it default to autorenew ON if you do this? If i bought something from anywhere else on the net i wouldn't expect to be charged every month for it.
They make it so easy to subscribe and buy stuff but a pain in the arse to cancel.