Upvote:9
The cancellation fee would have to be in their terms and conditions, otherwise they're pulling a number from thin air. Demand to see a written document which you previously signed (on check-in usually) which would indicate these terms. They can't make up terms as you go.
If you agreed to something in the terms, however, then yes, that's the agreement you made.
However, if none of these events were agreed to, then them holding onto your belongings without your permission could be considered theft.
Be firm, polite and request to discuss the terms in relation to signed documents/terms and conditions.