Cell C not honoring their feedback

On 24 December Cell C gave feedback, after a long conversation and then with a returned call to me, that indeed it is true that my contract is closed and cancelled. About 26 emails plus other written documentation, requests through their web system AND few telephonic conversations and the issue is still not resolved. On 14 Jan I discovered that Cell C black listed me.Though I am NOT in any arrears with Cell C, on 24 Dec I offered to pay an amount of R299 into their account just to close and conclude the matter. This was clearly stated not needed and NO BANKING DETAILS given to me. The whole issue Cell C, with every call from their side, though on my email requests to give details why they continue debiting my account while I legally cancelled the contract as per their procedures, were all just answered with the same, generic questions from different consultants, asking for details I have given several times in writing, even in my enquiry-logs and Cell C expect me to not become irritated/frustrated. NOW a paper trail is expected, while I struggled for a year to get ANY employee/consultant ANDThapelo to put anything in writing. Cell C has gone too far with *******ly black listing me