Reimbursment!

We booked a car hire through Thrifty on the 3rd October 2017. Unfortunately, due to unforseen circumstances, we had to cancel the booking. We were told in writing that we would be refunded in full. The refund was suppossedly done on the 25th November 2017 and I was told it would take 7 to 10 working days. However, nothing reflects in our account nor is anything pending. We have checked our bank statements, been into the bank and have phoned our bank as well as Thrifty numerous times over the past two weeks. This is becomming very frustrating and annoying as we do not know what to believe any more. Help!!!!