Mtn ********** Upgrade

In April I received an sms that my data contract had been upgraded. I immediately called mtn to let them know that I did not authorize any upgrade and didn't even speak to any of their agents to agree into an upgrade (I saw a missed call the previous day, and checked on trucaller that it was an mtn number) they have now taken R1200 from my account, so I'm being charged for a phone I don't even have with me. I've tried numerous times to call I keep getting told the supervisor needs to listen to the call, it's taking 2 months to listen to a call. To this day she's still getting to listening to the call, in the meantime money I can't afford is being taken from me. I am beyond frustrated with this company and regret ever taking their products. Their customer service is non existent.