Incorrect part received and taking a while to give

I ordered a part from Volvo after supplying vin number etc. I paid upfront as is the custom. When the part arrived I discovered it was the incorrect part. I took my old part to the spares dept to be told they can't supply the part I am looking for. I then requested my money back. Funds should have been paid in on Thursday but have now been told they are only prepared to look at it on Monday. This is unacceptable as I had paid upfront and expect the same or at least 24 hoor later response not for me to wait until its convenient for them to refund the client