DEBIT ORDER NOT ABLE TO STOP

I've helped my father in law to pay his account via Debit Order. He doesnt live with us anymore so he don't pay me back. It's acually my brother in law that should pay that account at this stage. Ive been asking the branch for four months now to stop the debit order and it still goes off every month. I cant afford that at all so I called head office last month and STILL NOT STOPPED. I withdrew my permission to use my bank account for his payments. THIS IS ***** AND IF THIS IS NOT RECTIFIED I WILL OPEN A CASE OF ***** AGAINST LEWIS STORES. JUST STOP THE DEBIT ORDER!!!!