Bad service

I bought a phone at vodacom in Parow Sanlam Center in Cape Town, the phone had problem with settings and the phonedid not even work when I tried to put it on, I returned the device the following day but they did not want to give me a new one as the policy states, they said they will book it in for repairs for 7 days, I went back there in Friday as they told me that vodacom has approved for me to get another device but now they told me that the same phone is not in stork, now I'm left with no phone and they can't give me any phone, the worst part is that this is a contract phone and I have to pay every month for something that I don't even have. Please assist.

Sgt Maguga.