Car rental deposit refund & incorrect rental exten

I took out avis rental car from Avis hatfield branch on the 6th march 2015 and paid a deposit of R1253 which is refundable to me as long as i bring it still in the same condition and with a full tank. My insurance company (Miway) booked the car for me. I later got an sms to return the car on the 16th march 2015 of which i did. there was then a pro-rada refund that was worked out. I was told to expect my refund back in my account in 2-3 days.Avis then debited my account the amount of R2370 and which when i enquired they said i have extended the rental car which i returned and was no longer in my possession. I enquired about this and the branch said it was a system error and they will fix it and should expect my refund in 2-3 days. i have not recieved anything to this day. When i enquired with the head office they say they can only see the deposit refund about which was pending (for the reason that i was not told). they also said they cant see any amount debited from my account. <br> <br>