Anyone with an on line automatic renewel with credit card for xbox live should be able to call xboxlive 020 7365 9792 or 0800 587 1102
listed price £39.99. Say you can get it cheaper by prepaid card approx £24.00 and they will reduce next years bill to £23.99. I have done it with no probems and still have 11 months left on my existing. A friend has also done it and will renew automatically in July for £23.99. May only apply if you have been with them for a while , but worth a shot.