UNAUTHORIZED DEBIT ORDER

I am fed up regarding Oakhurst's poor customer service. I have cancelled my policy with Oakhurst with effect from 02 July 2019 but to my surprise I received a letter of cancellation with effect from 30 July 2019. I called them to rectify their mistake and as usual they promised to rectify their mistake and I was provided with a letter of cancellation with effect from 11 July 2019 instead of 02 July 2019. Surprisingly this morning money was debited from my bank account. I understand why people are always complaining about unauthorized debit orders by Oakhurst. I attempted to resolve this matter with them and I am taking this dispute further. "STAY AWAY FROM THIS DAY LIGHT *******. I AM FED UP.