Bad service from Telkom

My fibre was installed 12/12/18. I was phoned by a Telkom sales person, to switch from Telkom Adsl to Telkom fibre. This lady was very helpful and arranged everything. My agreed amount was something between R700 and R800 for a 20mb uncapped fibre line. Which I agreed upon. When my bill arrived I was invoiced R1700 for fibre since December and every month thereafter. Telkom shops cant help me, I've been to the one in Festival Mall and Centurion Mall. Then I was given this nr ********** 250. The billing department says I need to phone the sales department. The sales department refers me to Billing. Now because I have a R6000 account which I'm not willing to pay as I was overcharged since December 2018 my services have been suspended!!!!!!! Is there anyone employed by Telkom that can assist me with this??????