Mistake

I have had my service with Telkom since August 2015. On my first month I did not receive a bill, so I called, to no avail, I was told to wait till the next bill. So I did, when it finally arrived in month three, I had made one payment. Then I get told in November that I am in arrears. On 14 December I paid the arrears amount and will pay the Jan 2016 bill on 1st January. My line was still suspended. I do except that I am a month in arrears, when I went to the Telkom offices on 2nd January 2016 I wanted to query the outstanding amount and total that needed to be paid. I was eloquently told that Telkom has made a MISTAKE and they did not charge me for the reconnection of my sim. This amount equated to R406.00+- and my total owing is R 1150.00+-. Now please may I understand how is it possible, that Telkom, can make a MISTAKE. But if I made a mistake and not paid my bill in 2 months, they will be quicker than a flash to disconnect my line. Now that they have made a mistake, what will be the consequence? Do I get to keep my line open till they rectify the problem? Will they reconnect my service? will they discard all reconnection fees because they made a MISTAKE?