Phone customer services (01604 230 230 and keep pressing 0), and tell it you want to cancel your card. This will almost certainly lead to an attempt to convince you to keep your Barclaycard, either by the customer representative you speak to, or they'll patch you through to the 'Customer Retentions' department. Reports suggest the current lure to keep your custom is short term cashback deals of 2%, 3% or even 5% lasting three to six months.

If you have said you want to cancel, not got the cashback and are having second thoughts; don't feel obliged to go through with. Simply say you want time to think about it and you'll call 'em back.