Telkom Harassing 85 year old pensioner

A number of years ago, Telkom offered to a product to retain my landline number that they wanted to discontinue. I agreed and Telkom sent me hardware via a courier. I then found out that my old number could NOT be retained and Telkom said I could cancel. I returned the equipment via Telkom's elected courier, unopened. Since then telkom keep hounding me for payment despite me contentiously sending proof of the return of the equipment & Telkom acknowledging my case has been resolved. Now debt collectors keep phoning me. I am 85 years old and the won't leave me alone.