CELL C NOT UPDATING MY CREDIT/ legal number not working

had arrears with cellc and they sent me to nudebt collectors to collect on the cancelled contract. An agent from them called me Jan 2019 notifing me that i have R56 left on the account and sent me banking details. so i then called cellc so that i can get a settlement letter from them. customer service knows nothing about my account and they pass me to legal and for 2 weeks been on hold for 3 hours and nobody picks the line up. i have now another debt collector collecting on the account that i have settled. i need my name cleared with ITC. you guys are ruining my credit health. customer service agent know nothing and they never have a manager to talk to. **********