Poor service

My car was booked in for repairs on 2 of Nov 2015. My insurance arranged a rental car with Avis of which I collected on 5 Nov 2015. I paid in a deposit with my credit card. I drove the car for 7 days only and returned the vehicle back to Avis on friday 13 Nov 2015. They said a refund for my deposit will be paid back to my credit card within 4 days. I gave them a grace period of 7 days and there was still no refund. I then phoned the sandton branch, they gave me a call centre number, I called it numerous times of which in a few the line will cut off without getting through to someone who could help. I eventually spoke to a lady from the call centre who said she'll request a refund manually, she asked for my credit card number and assured me that it will take 2 working days for a refund. To date 19 days later, my deposit refund is still not back in my account.