Warning about Cell C and faulty phones

I took out a new contract with Cell C in the beginning of January this year with a Sony Xperia M5. The M5 has a problem in that it switches itself of sporadically (when the battery is still charged) and then will not switch on without being connected to a power source. This is a common fault which can be read at [URL Removed] I returned the phone as an out of box fault within 7 days and when I submitted the phone it was in perfect condition. Now two weeks later when I returned to the Menlyn branch of Cell C to enquire about my phone, they reported it had been rejected and sent back due to a scratch on the back. There were no scratches when I submitted the phone. I am under the impression that they intentionally damaged the phone to avoid having to exchange it.<br> Regardless I am now stuck with a phone that switches off randomly and they say there is nothing they can do about it. In terms of s55(3) (read with s20) of the Consumer protection act, I can return any goods if it is not suitable for the particular purpose. Clearly a phone that switches off and will not switch on again does not meet its purpose.