Been waiting for days for a reply to my account

I want to canel my account as Cell C service is pathetic and weak! I want to pay my account in cash and they refuse and say only debit order, I told them that time the debit order charges are killing me and want to pay cash every month, but the reply was that it is mandatory. I then requested for the cancelation amount so that I can cencel my account as I am truly unhappy with the service, I was then after a few days notified that I will be contacted in 2 working days time but was only contacted 11 Days later! I want my fulle amount owed so I can cancel this stupid account immediatly!