12 days later still no refund

I am very disappointed with the service I'm getting from Avis, my car went in for repairs on the 20th Jan my insurance company referred me to Avis for a car rental and on the 22nd the car was returned to Avis as my war was sorted. I was assured that it takes 48 hours to get a refund, today its 12 days later, I called them on the 30the January I was told to wait another 24hours I asked after waiting for a whole week? This morning I checked my account again still no refund, the question is will I ever get my refund, what do I need to do to get my money back!