Useless repair centre

I upgraded my contract in July 2015. And from about 2 weeks after getting the phone, the screen kept going black. I have taken it back and forth to Vodacom repair centre 3 times already and each time it works for a little while then starts again. In the mean time my account is debited every month. The phone has gone blank again. So the phone is on but I cannot see anything on the screen. The phone is less than a year old. I am not willing nor do I have the time to take the phone back for the 4th time. Vodacom needs to take this phone back and give me a new one. Moreover, when I took the phone in for the 3rd time, my camera got damaged by one of the technicians and it never worked well again. I refuse to keep paying for this bad service and trust I will be getting a favourable response.