Europcar Refuel Fees

My insurer rented out a car for me from Europcar. I returned the car with a fuel tank but was charged refuelling fees. I reached out to Europcar for assistance and showed them my receipt for the refuel. They acknowledged this and sent a statement with a refund for the incorrectly charged refuelling fees. It’s been over two weeks and I still haven’t received my money. I have reached out to their branch several times and keep getting empty promises.