Cell c contract

I had a contract with cellc and apparently it was in arrears, they never called me to inform me it was in arrears. I did not notice they they have met deducted as I have 3 more other contracts and they the same amounts. Right they handed me over I understand, but I have been battling to get hold of the company where they handed my account to. I tried to call cell c back to assist me Witt settling this account but they refused and have been ignoring my numerous emails. I have been struggling for more than 2montha going onto my 3rd month and it's negatively affecting my credit score. What should I do to get them to help me settle this ***