Write a Letter to the Bank informing about the loss of your debit card and request for replacing it with new card.

Hello,

Re: Account No. <Number>

This is to inform you that recently I lost or misplaced my <type of card> card on the above-referenced account. The lost card bore the number <number from card>. I request you to cancel that card and issue me a replacement card as soon as possible. It is urgent that any further use of this card should not be authorized under any circumstances.

I would appreciate your prompt attention to my request. If you have any queries regarding the matter, kindly do not hesitate to contact me.

Regards,