MTN deducting more than what the contract says should be deducted.

I took 2 Samsung A32 phones in June on a two years contract and the amount agreed on is 499 per month. To my surprise month end June they deducted 858 and in July they deducted 927.

I called the store where I bought the phones and they logged a call and immediately I received an email that they logged a call and after few hours I received another email saying the case has been closed without anyone calling me. I have been logging a complaint online yet no one is contacting me. I want MTN to fix this problem and refund the extra money they have been deducting.