Gave my phone to someone else

I have a cellphone contract with Cell C as from February and in one months I broke the screen took my phone for repair and got charged R1300 which I paid but when I was about to collect my phone I was told that unfortunately someone collected my phone. That was in Fourways mall. I don't understand how was that possible, I was told to come and check my phone after 7 days.<br> <br> I wonder what measures do they take in store to make sure that right people get the right how can you give my item to someone else while you took my details down. I my self bought the cellphone to a different service provider because I had bad experience with Cell C but I was convinced enough that this time things will be different but I was just fooling myself, I WILL NEVER EVER BUY ANYTHING FROM CELL C, I will to to see the measures that I need to take to cancel the contract!