Account type changed

In February this year I changed my ADSL line rental from Telkom to Mweb. After some initial confusion, with both Mweb and Telkom charging me for the line rental, the problem was rectified and Telkom credited me for the line rental portion. However, they started billing me for calls (backdating to February) that were always free as I was on a closer deal where the calls on weekends and evenings are free. My in-laws also changed their line rental to Mweb and had no problems like this. An email to their billing department on 18 May got no response