NuDebt not Responsive to Correspondence

Telkom have referred a Mobile Contract account to NuDebt for collection because they believe that I have received services not paid for. This is not the case, and no matter what I send to NewDebt in support of my claim, they persist in pursuing this matter. The reference number for my visit to the Telkom Offices to cancel Telkom LTE Contract Telephone Reference ********** 2 (for Nudebt), is ********** 6, on an email from Telkom dated 1 December 2016. Despite several emails to both ********** and ********** I have not been able to resolve this problem.