Yes, you can cancel a Direct Debit. The mandate form given to you by the Service Provider / Creditor will specify the number of days’ notice required before you can cancel a Direct Debit. Simply write to your bank or savings and Loans company. It is also a good idea to send a copy to the organisation concerned.
Remember that cancelling the Direct Debit simply stops the payment to the organisation. If you carry on receiving the goods and services then you will have to agree an alternative payment method with the supplier.