National Security - **********ly taking my money

I cancelled my contract in January 2022 and paid the final settlement figure to cancel my contract in full and final settlement. This was confirmed in writing by National that my contract is now closed. Now 7 months later out of the blue National debited my bank account. I emailed them on two occasions and have still not received a reply. National to me are a bunch of ******, **********ly taking my money.