MTN Service failure

I took out a wifi month to month package of R429. I received a call from a 3rd party company on behalf of MTN, Pre-advantage. This lady forced to make a sale out of me, I declined everything she offered. After our call she went and changed my wifi package to a useless cheaper package. I have been in and out of different mtn branches, calling them and even emailed their CEO Ralph Mupito. A week later and my problem is still not resolved. My account is being debited after I paid the correct amount of R429. The latest communication I had with mtn was yesterday where I was told to call pro advantage to fix their mess. Mtn must take liability for service failures made by 3rd parties calling customers on their behalf. I have never ever been so disappointed. I hope mtn gets rid of all the *********** staff members as well as this unnecessary blood hounds forcing customers to make sales. Please sort out my problem MTN it's been a week and your useless staff can't resolve my query.