No refund after a month

We took the car back on the 26th of March and was told that since the deposit had been paid using my wife's debit card they will refund it to her in 3 days. It has been over a month and we have still not been refunded. every time we call we get a promise to be call back however we don't get any call-backs. How long does it take to refund the deposit, surely it cant be over a month