Dear :

This is to advise you of the cancellation of our Purchase Order No. for [products]. As I explained in our telephone conversation on [date], our sales of these items have slowed down during the past months and we won't need to order any more until [month]. You can expect a new order for the same amount of these items by then.

Sorry for any inconvenience. We appreciate your understanding and look forward to more business with you.

Sincerely yours,

[name]

[title]