Faulty Phone That Vodacom can't repair

This is my second complaint about the same issue. I have a Samsung S4 mini. I got the phone in September last year I only used it for about 3 or 4 months. The first issue was that it stopped working I could not Dail at all viacontacts or when I insert the number I also could not see my contacts.I took it to Vodacom repair in Alberton they were able to fix the problem but the phone could not pick up network at all I noticethis when I got home. I took back and they said that I must test the phone as in insert my sim in another phone and see if it works when I did that at home the sim worked properly. When I inserted a different sim in the S4 mini it didn't pick up network at all meaning the fault is with the phone. I have been paying for a phone that Iam not using at all because your technicians and call centre staff are unable to help me. I took the phone in again 3 weeks ago and I was only able tofetch it this weekend and guess what it's still not fixed. I want a new phone and 3 months to free if not I cancel my contract with Vodacom if that's not possible I have no option but to involve my lawyer. I have all the documents of all the times I took the phone in