HARASSMENT BY COLLECTION AGENCY

this company keeps calling me and sending me SMSes for money I do not owe Telkom, I repeatedly tell them to stop calling and not to institute charges as I do not owe but they will not listen. I must provide my ID number, meanwhile they call me and I must go to the police and make an affidavit to say I don't owe. Why must I go to that trouble when they are the ones who cannot be bothered to ask Telkom for proof of what I supposedly owe, which is NOTHING