Customer service nightmare - 5 weeks (and counting)

I have booked multiple times with Budget and unfortunately this last time was truly the worst experience. From getting the car to the customer service I have been battling with for 5 weeks now.

I had booked a car seat for my baby, the first one they gave me was for the incorrect age. The second one was such bad quality that my child screamed her lungs out every time we drove in the car - I called and asked for assistance from the closest branch and they were not willing to assist.

A few days after my holiday I noticed an additional R3972.33 taken from my account (my booking was paid in full online). I called customer service and was told the trainee who assisted me at the branch did not allocate my online payment and that I need a refund and she will keep in contact with me. 2 weeks later no update, I called again and go through the WHOLE story again and dealt with Nothando Mtshali - again same story and promised she will keep me updated. No update, I emailed her no reply. I called again today and spoke to Tendani who assured me that Nothando will call me today after she is off her phone call (did not), and Tendani himself will check in with me in 1 hours time (did not).

HOW DO YOU GET YOUR MONEY BACK FROM AVIS WHO TOOK IT IN ERROR?!