Unauthorized debit order

I am sad to say that i have been working nicely with fnb until i take up lifecover with them, i was on maternity i asked them to start debiting me in December as i did not hv money while on maternity, they took money that was supposed to help me with the baby when i queried they said they will call me after listening to the recording, please cancel that life cover n return the money that was debted after i queried the debit bcz u did not come back to me.