Sales Blunder

I have upgraded my service from ADSL to Fiber about two months ago. I was told by the sales agent that the service will remain as a 2mbps line but will now be using fiber. The cost is to remain the same. I have received the latest statement only to find out that I am now being charged more than 50% more per month. I have logged a dispute on the 15.11.2017 (reference - ********** 8) and was called back today (21.11.20170 and was told that they cannot assist me further as I now need to change my package first and only then this can be investigated. Further to this I am now being told that the fiber starts at 4mbps speed (contrary to the information given by the sales agent). Why must I continually at my cost call Telkom repeatedly to sort out an issue created by them.