Santam - does being a big insurer give you right to bully small usiness?

I want to pull my hair out! For 5 months now Santam keeps debiting my account with insurance premiums that were cancelled via my insurance broker. Every time there is another excuse, in the meantime +- R1,9k is debited to the ban account. This is so unacceptable that businesses can send debit order instructions to the bank even after having been informed of cancellation of services!