Dear :

Last Monday I made reservations for [number] single rooms in your hotel. The dates were from to . Unfortunately, the meeting in [location] was cancelled and there is no need for our managers to go to [place]. For this reason, we have to cancel the [number] single rooms we have reserved. We will make new reservations when the meeting is rescheduled.

Thank you very much for reserving the rooms for us.

Sincerely yours,

[name]

[title]