Mtn bad customer service

I've been called by Mondo cellphone contract to take a contract with Mtn. I was told that I would be paying R99 per month but mtn is charging me R199 per month. I've Been contacting Mtn almost every day to query this and I am not receiving any feedback. Bad customer service. I've even told them to listen to the recording of the conversation but they are not getting back to me. I want to cancel this but they are giving me excuses and making me sound like a ***** ,is this how u treat customers?