Telkom billing

After waiting 4 months for my ADSL line to be installed and being told that the cables are ****** (which eventually we found out from the technician this was never the case), my line was installed on 15 August 2018. I received a invoice for billed items, free devices not discounted, calls and services from May 2018. I logged a dispute on the 15 September 2018 to date I have not received a call from telkom or correction of my invoice. I am being charged interest on the above mentioned items every month as I refuse to pay for services not received. My credit score since has also been affect as each month after I pay my contract amount it still refIects that I owe telkom R3 500. I have been logging online disputes subsequently I receive sms's saying its been resolved but to my dismay. I have also been calling their customer service line atleast every second week and everytime the agent says the matter is being escalated to their manager someone will call me in 5-7 working days to my dismay. I have received nothing but pathetic service from telkom from day one. Its been 5 months later and the same problem persists!