Their Legal Dept number is always engage

I had a contract phone with Cell C and paid it off in 24 months as per contract term. After I had paid it off, I started receiving statements that said I took a new i Phone and I had to pay R500+, I called Cell C & disputed this they gave me a reference number & I kept on calling them until they told me the matter has been resolved & they are aware I never took this contract. Now after a year+ I discover that Cell C has blacklisted me, every time I try the number they gave me *** as Legal Dept it is always engage. What do you do as a person being punished for something you did not do? Hey Cell C