Nudebt refuse to investigate credit on account

Nudebt added a trace locator to my Credit Bureau profile to a supposed \default"payment for Telkom Mobile Ref ***. I tried to give Nudebt reference numbers to verify that I do not owe their client any money. Nudebt refused to accept it and said Telkom Mobile has handed my account over for collection on 2 Dec 2015. Nudebt intimidates and threatens me by sms. They refuse to investigate my case and account. The fact is that my account has a credit at Telkom Mobile which cannot sort my billing issues from November 2014 until today. I have more than 6 open cases with Telkom Mobile. As a business man I cannot have any credit listings against my name. I demand written apologies and verification that my name and credit rating is clear. Please HELP !!!!!!"""