No response after handing in handset to cancel con

I received an SD406494 reference number to cancel my contract due to a very bad network issue. I then went into Cell C the Glen store and handed in my handset on the 30 August 2015, in order for the contract to be cancelled before the end of September. Yet I have received NO response from Cell C about receiving my handset and NO response on 3 calls I have already made to the call centre asking them how far this cancellation is. I want this contract cancelled so I can enter into another one and STOP paying for NO service!