Unfair and bad customer service

I traded in an i30 on the 31 of August at Arnold motors,I was told that the bank has approved me for a GWM H5 2015 model,I took the car then drove it and discovered that it has too many faults,I took it back the following day,telling them that I am not happy with the car but they refused to change it for Me,On the 22 of September Johan Rousoul phoned me and said they need the car because they did not take it to the test,I was going to Mpumalanga that day ant I requested them to give me the car before 12h00 am but they never did,they Saud they are going to fix the car untill today I don't have the car and I haven't payed my first instalment,they said I will get the car on the 3rd or 4th but I never got It,I am now using taxis and I feel that at the end month it will be unfair for me to pay for the car that I did not use and they are not even communicating with me even today,I feel that I don't want the car back even if they fix It,I have been ill treated and given poor service,I want nothing to do with the Arnold motors people