Mr price mobile sim

I opened a Mr price account a few months back and I was given a Sim card which I was not informed that it will be loaded with airtime and data every month and that money will be added to my monthly payments. My monthly installments kept increasing even when i wasnt taking anything anymore using my account, i only found out this month from their Agent that it's because of the Sim card. When I put the Sim card for the first time on my phone I found an airtime balance of R871. This is day light ******* I never agreed to that deal and I don't need it.