unhappy client

I have been a MTN client since 1995 and for the last 5 years I have been having problems with the service, not to mention how long you have to hold on for the call center. I have taken out 2 contracts last year for my children expected to pay R600 as contract per phone was R299, however there is an extra amount deducted which I did not authorise and requested more than once to change the limit but keep hearing that it cannot be done need to be done when account bills, this means I will keep on paying extra R200 on my account. There was a contract that was paying for 3 years and when my final date of payment came which was November 2021 MTN still deducted another premium in December and January 2022 raised queries and to date nothing was done to resolve. I am really frustrated with the service received by my service provider and need action taken.