Being charged more than expected

I opened a funeral cover with standard bank last year on the first 2 months they took the correct amount that we agreed on after that they started taking more than what we agreed on when I called to cancel the policy they agreed that they will cancel it to my suprise they didn’t cancel it and now this month they have debited the money 3 times from my account and they telling me that they can’t reverse the money I hate standard bank and am going to change my bank to another bank