Defective Goods Sold - Bad Attitude!!!

In January this year we took out a contract via cell c for my mum. This was a smartphone contract, Galaxy S3 mini, with a data bundle inclusive. The data services on this phone never worked from day one. We took the cellphone back to the cell c store on 3 occasions. They did a sim swap and informed us that the phone would work the next day. It never did. Eventually we were informed by the cell c contracts department that the phone needs to be beooked in to their repair centre and then we can decide whether we want to cancel the contract or not. We did just that. We received the phone back and it still does not work. We asked cell c la lucia to cancel the contract. They refused stating that the phone needs to go in for repairs again for a second time. At this point we are very frustrated and just want the contract cancelled and NO cost to us WHATSOVER as we were sold a faulty handset. The phone number in question is ***