Vodacom / MBD harassment !

Hi I happened to have this account with Vodacom that i was not aware of and only realized when i received a call from one of their consultant in November 2018 that i owe them. I did explain that i know nothing about it and was requested to send an affidavit and a certified ID copy .which i did not just one but i have about 30 emails to sent to them.

Nothing has been done , i'm still getting calls and SMS's from MBD which is the collection department for vodacom , threatening to take legal steps if i don't pay the account. Lately they even hang up on me as soon as they realist that they have called me and i always say to them that i am still awaiting feedback from their investigation department. Please assist me !