For clarity and to avoid misunderstanding, there are differences under law between direct debits to bank accounts and direct debits to credit cards.
The long version of the discussion is at this thread about Cancelling direct debits linked by @grahroll above.
A synopsis is that a direct debit to a bank account can be cancelled by notifying the bank and it is correct that any bank staff stating otherwise is either ignorant or lazy. It is a ‘one letter’ process.
OTOH a direct debit to a credit card account has to be handled differently as explained at moneyhelp. It becomes a ‘two letter’ process with a potential follow up to charge back unauthorised debits. The important text is
To cancel a direct debit on a credit card account, you should first write to the organisation with whom you have established a direct debit, instructing them to cancel the arrangement and send a copy to your financial institution. If the debits continue you can then request your financial institution to reverse the transaction as it is unauthorised.
Often direct debits from a credit card are linked to a contract for goods or services which you have purchased and it may be a term of the contract that you pay in this way. You could therefore be in breach of your contract and should seek legal advice before doing this.
