Breach of contract

Recently, my wife went to your Woodmead branch and were advised to get the Samsung S5 mini over the iPhone. We took the phone out the box a few days later, set it up & realised that it wasn't connecting to your network. We then took it to your Vodacom store in Eastgate, where they told us that we needed a new Simcard (R70), even though the one we were using worked perfectly well our previous smartphone. The next day, the phone still didn't work so we took it back to your store in Woodmead. The lady then adjusted something on the phone and it worked for that hour, but then stopped. We then took it into your Vodacom repair centre in Sandton City, where they did a software update, which didn't work so we had to take it back. Then, instead of just giving us a new phone they, and I quote, 'fiddled' with the antennae. That worked for 1 day, and then the next day it lost signal again. So, we took it back. This time, my wife got an SMS stating that we owe R1800 to replace the PCB board. After calling the service centre, they claimed that this was because it is the 2nd time they replaced the board (which isn't true). As this is a new contract & phone, we wish to cancel it & get a new iPhone