MTN phone Contract

I Sinethemba Bomvu From Eastern Cape at King William Town, I took a phone contract with MTN at King Williams Town branch in July 2020 according to my contract I suppose to R350 per month to my suprize they debited R1190, I went to MTN branch at King williams town to report the matter they said to me it was a mistake and they promised me to correct their mistake in the following Month. In the following Month they debited R980 I went again to them they asked me to bring my bank statement so that they forward it to the Manage they promised to get back to me with response, while i was still waiting for the response it continued deduct the same amount. I never got the response I decided to change my bank I was so disappointed with the MTN conduct so I need your assistance