MTN CONTRACTUAL MOBILE PHONE AGREEMENT BROKEN

I have been a customer with MTN for many, many years . In March 2024 I had to upgrade my mobile phone. I signed contractual agreement was made with an agreed amount per month. Since then every month they have over charged on the agreement and every month it gets more. This is completely ******* as they are breaking a contractual agreement. I have repeatedly emailed them to only get responses not solving the problem