Client has to pay for MTN's mistake

Good day I had 3 contract with MTN then last month (June 2019) I called MTN cancellations to please assist with cancel the cheaper contract then the consultant said I had to pay R187.71 to cancel the 2 lines, I did as advised by the MTN consultant but on the 21 June 2019 I received the email saying MTN will take R2181.96 for the early cancellation then I called MTN cancellations I was told it was the MTN consultant that made a mistake on advising me with the settlement amount I then asked them to please re-activate my 1 contract that had a huge settlement till today I have not been assisted where as Randall said something that made sense to me when I called last week but yesterday I spoke with Portia she told me I have to pay for MTN's system mistake and she promised to call me today before 12:00 but I still have not received the call from Portia or any one from MTN. Please help me.. Thank you