Bill dispute with Telkom

I am a 74year old pensioner who took out a contract with Telkom in 2015...it was a phone contract and data with wifi at 20Gb day and 20Gb night for a cost of R389 a month. In May 2019 I was called by Telkom and they had discussed with me that they will be changing to huwaie smart broad band modem because of cable theft of copper...they further discussed with me that I will not pay extra and contract will remain the same . At the end of September 2019 I received a bill of R5000 and when I queried it at telkom a gentleman at the bluff branch sent a note to telkom discussing my concerns and inaccuracies of this bill. After numerous up and down to telkom no justice obtained, they always say their lines are down and that they cannot assist . I have a reference number that was open and closed without sorting out my dispute. My bill now stands at R7423,92c. I am not sure how as a pensioner I am suppose to cover this bill that I did not make, no assistance from Telkom whatsoever.