MTN South Africa doing me dirty with its so-called service champions

MTN South Africa did me dirty on a cellphone contract that I app**** for online on October 2022. The contact was allocated to someone else on claims that I wasn't using it after buying the phone, but what was supposed to be a fixed contractual amount kept on increasing month by month. Since the cellphone contract got merged with an existing sim-only data contract that I've app**** for at MTN Middelburg Mall (Mpumalanga), I visited the store for my problem only to be advised to call customer care although I had an existing sim-only data contract with them. Calling MTN South Africa customer care proved to be fruitless although they call themselves so-called service champions. MTN South Africa please sort out this mess that you've put me through