Have the dates you booked for the stay already passed? If not, sometimes a workaround is to modify the reservation to a future date and then cancel it.

If the dates of the intended stay have already passed, you can still try calling the hotel and politely asking for them to allow you to rebook for the future (or perhaps even cancel). This is entirely at the discretion of the property. Sometimes asking nicely works. It doesn't hurt to try. Good luck...

--Jon

P.S. Whenever possible, it is always best to call in advance of stay. Your chances of success are greatly diminished if you wait to call until after your stay would have been.