Help me fight against such things even for the next customers

Hi I opened my account since 2021 and have been paying for the account in a good way have never had any problems regarding my payments, Mr price gave me a sim card from the their store and the sim card has not been working I called for cancelation the made me wait 40 minutes on the call and they did not help me they usually take R99 from each time I pay for the account and my money is always going up not down, pay right on time now I asked them for my refund because I pay for the sim card each month but it is not working since the day I started to pay for the account my refund should R2000 or more counting from 2021 until up to date how am I suppose to pay another amount of money while they owe me so much and not helping? I want my money back so I pay for their account and close it I no longer want to be their customer please help in this case