If you authorized the bank to make the transfer to the merchant on your behalf, you need to revoke your authorization with the bank.
You will need to notify your bank at least three business days before the scheduled date of the transfer and inform it that you wish to stop payment. You can provide the notice orally, but the bank may require you to confirm the request in writing. If the bank requires written verification of an oral notice, it will provide the address where the confirmation should be sent. The oral request will not be effective after 14 days if the bank requests written confirmation and you do not provide the written notice. In addition, a written stop payment order often expires after six months. It can be renewed for another six months.
If you authorized the merchant to charge your account and you want to stop the merchant's ability to debit the account for future transactions, it is a good idea to
contact the merchant in writing and revoke your authorization to charge your account;
keep a copy of your notice revoking authorization to charge or obtain a cancellation number; and
notify the bank that the merchant no longer has authority to debit your account. Provide the bank with documentation of the written notice.
However, the law does not require you to notify the merchant for a stop payment order to be valid as long as you have notified the bank. If you have revoked authorization and the merchant continues to charge the account, you can dispute the transactions with the bank.