Very Disappointed with Service

I am a customer of Telkom for the past 20 years ain December 2014 I upgraded my Adsl modem and my adsl line to 4meg line .With this package I was given a Telkom Free sim card with R50 airtime and a ****le for my computer with 500megs of Data. The total bill of this account is R589 and I don't Pay for calls cause I have unlimited Telkom to Telkom calls on this package. I January this year my bill came to over R700 and I went to query it at a Telkom office in Gateway and they sadi I am being charged for calls from my cell phone with the Telkom sim card .The agent looked into my profile and saw that the sim card was an closed line and I could not make any calls if the r50 airtime was finished. They then refunded the cell phone amount. The next month the same happens and I am back at the store to query this again. They checked the system and refunded me .I month goes pass and it happens again. Why is Telkom charging me for a sim card that was issued free to use. Had I known that Telkom lies to their customers and then start charging them for stuff that they say is free, I would have not upgrade my package. There is somebody that is charging me for calls I should not be paying for .I ca