Unfairly blacklisted

I was paying my bills without skipping one month and now i'm blacklisted. <br> The account is up to date according to my deposit slips from Nedbank key west (proof of payment).<br> I was due for an upgrade on my contracts on the 1 st February 2015 but due to the blacklisting I could'nt do so. <br> Cell C phoned me and ask if everything is still good for the upgrade on the sunday and I said yes, on the sunday when I got there there was a probleme with my account and this was the blacklist. They said I must come back on the monday the 2 Feb 2015 to get the contract done, I got there just to here that i\m blacklisted. I faxed the proof of payments to them but nothing happend untill now. Each time I phone cell c they say they will phone me in the next 5 min but they don't get back to me. "