Groupon failing to refund after promise

At the start of June my wife paid over some money to Groupon for a promotion, she realized she had made a mistake by mixing up the reference numbers and immediately contacted Groupon to inform them of her mistake, turns out that the promotion didn't have any immediate bookings available and she would have had to wait about 4 weeks for an appointment and therefore asked Groupon for a refund. Several calls, emails and growing frustrations later and my wife is still waiting for a refund. Groupon has now promised her that the refund would happen about three weeks ago and we still have not received the refund.