Telkom no more

I am being harrased by Telkom for an account for which I never signed a contract. This apparent cellphone contract is nowhere to be found, and I am left with a bad name because of an ******* debt against me. Telkom is simply refusing to assist me since 2013. Their consultant has indicated to me that I will have to prove that I don't owe them. I requested the signed contract, and have not to date been provided with a contract, or proof that I ever received the device. I am really frustrated with this situation...