Cancelling/Closing Cell C Account

I got a letter from Cell C that stated that my account is paid up and they advised that they will speak to the relevant credit bureau's to clear the mishap. It's been 6 months since receiving this letter and my name is till not cleared. When I check my credit score, this account is still active. I've called numerous times and even sent an email recently and I still haven't received a response. I really don't know what to do now.

If possible, please avoid getting a contact with them