I am being abused by Vodacom repairs

On 28/01/2016 I bought a Vodafone tab 10 device cash at sport scene store and in March the phone started giving me problems so I returned it and was told to take it to Vodacom repairs they will fix it because it is still new . AT Vodacom they took the phone and I was to be contacted to come collect it. The next day I got an SMS saying I must come collect it and I went to collect but they have already given it to someone else so now I had to wait for that person to return it so the whole of last week I had to go to Vodacom just to be told to come tomorrow until Saturday they gave me a tablet that was not working and I refused to take it and was told to come back Monday. Yesterday they gave me the same phone that is not working and it is still not working now I'm completely clueless on what to do. Can someone please help me I'm tied of going to that place they make my blood boil and I'm really close to punching some one because all I want is a working phone