Noise coming from the back when car reverses

I bought a brand new car in Feb , Polo TSI Highline DSG from McCarthyVW in Arcadia within a week the car already had a problem , I took it back they told me it needed alignment they did that and the car was ok for a while .After sometime the car started having some funny noise when I reversed. I took it back they told me they cant diagnose it . I took the car I left . The noise was still there , took the car to them for 15 000km an told them about the noise, even explained how it happens and how often it happens I fetched the car , they told me they couldn't find anything. Now we are .No I am fighting for them to take the car back, provide a courtesy car until they resolve the problem. They told me they understood and they will get back to me. I gave them time and nothing happened. I sent an email both Jimmy and Stephan (dealer principal) didn't respond. I called Jimmy said he will get back to me I had to force him to commit to when he will get back to me, I have been trying to reach Stephan from the morning with no luck and I called the sales person ITU who promised to speak to them but now he is not taking my calls or responding to my smses. Sent them another e-mail this afternoo