Telkom ***** and **** / Nudebt threatening me

I canceled my internet (DSL) contract with Telkom at 01/Nov/2017. (Document excited) And I pay all invoiced.

From last week I received the sms from some company that said I must pay R1400 because of outstanding payment?!!!!!!!!!!!!!!!

I called them and said to them send the outstanding invoice of telkom to me but she said we do not have it, only system show you must pay this amount.

I will go open the case of ***** and **** for telkom and I will go open the case for NuDebt that send threatening sms to me about legal action.

Is not possible I receive sms and ask pay money without any backup document then threatening me.

Telkom and Nudebt effect on my safety.