MTN *****/ theft

I got a call from their call center for 80Gigs of data at R15 extra on my contract. The debit order that went off of my account for the data was over R300. They changed my entire contract and took all of my minutes away. I have been trying to contact them for over a month. But the response is nothing that can help resolve the issue. The CEO was also in the mail and not a this was done. MTN is literally Committing ***** by lying to their customers!! All of their helpline has been tried even going into a store. The 135 number they give you to call nobody ever answered