Can't repair phone

I collected my phone yesterday (Thursday) from Cell C after handing it in for repair a second time and already (Friday) it is not working!!!<br> I received a new phone in December but I have not had the use of my phone for the last 3 months as it has been in for repairs twice now for 3-4 weeks each time. I'm paying my monthly subscription but I'm not able to use what I'm paying a lot of money for. I would like to give back the phone and cancel my contract as Cell C are obviously unable to repair the phone. I also want my monthly subscription refunded as I have paid for a service that I was not able to use through no fault of my own. Please advise how I go about this. Thank you.<br>