Unacceptable Service

I bought a new Samsung J1 on the 22.05.15 all was great but eventually the phone had so many fault that it had to go in for repairs. It was booked in on the 08.07.2015. They could not fix it so it was sent to the JHB repair center. They replaced the PCB and the screen on the device. I got the device back two week later. Two weeks later it all started again.This time they had the phone for almost another two week. I got the text telling me to collect my phone. So off i went only to be told that the phone had not been repaired. this was due to IMEI mismatch on the PCB. Now it was MY problem. So I left phoneless again. They had the phone until the 29.09.2015, a full month. Guess what it has been with me for two weeks and the problems have started again. I called the service manager, he is never available. He never returns calls. Now i an told to book phone in again. NO i want my phone replaced, no more trying to repair. TAKE RESPONSIBILITY VODACOM.