Contract cancelation

My name is Ziyanda Maseti i had a contract with telkom and it was ending in april this year. I settled them in april this year. I called them in may for my contract to be canceled as they continued to bill me. The agent that was assisting me said i need to make a payment of R100 then they will cancel my contract. They continued to bill me still i called in again onother agent that assisted me said that the matter is escalated to their collections department for them to reverse the bill it was R200 at that time and they will cancel the contract after. She even advised i will recieve feedback with in 24 hrs and i did not receive any response. I called in again in august the bill amounted to R500 the agent that assisted me she even gave me her email to do a follow up if i don't recive feedback. I wrote an email to her for feedback her email is *** and she didn't respond. I called in again the agent that was assisting me said that they are still investigating and on their system it has been highlighted as a new incident but i have logged this matter in may. I no longer have their sim card i am not receiving any prepaid from them i lost that phone in 2018 but i paid them in full. My reference with them is ***6 and my id no is ***. Please help me they keep on billing me R100 a month for prepaid that i am not receiving. I took their contract in 2018 it was supposed to end in april 2020 and i was paying R300 a month. Now they are charging me R100 for prepaid i am not receiving.