book in cell phone 3 times with in 6 months

I took out a contract las year from cell c in december wen I gt the phone with in the first 7 days I book in the phone for repairs becuz of it was over heating wen I receive my phone back they said it was fine . Wen I get home I noticed its still doing the samethin so I stop using the fone 4 abt a month .wen I took out the phone 2 use it was still doing the same thing so I left it .then the battery run low on the phone wen I try charging <br> The fone gt very hot and the back cover and battery unit gt burn so I book the phone at cell c and they repair it wen I got my phone back the back cover was nt replace and my front buttons were nt working so I had 2 rebook my phone in the same day. From the time I got my samsung s4 I did nt use the phone . I am really not happy with the product and service I gt from cell c I would like to cancel this contract becuz its would in 6 months my new repair number is PRE 620507