You can cancel a booking at any time directly from your messages.
Here are the steps:
Go to the Inbox tab in the app.
Open the conversation related to the rental you want to cancel.
Tap on the three dots (⋮) in the top right corner of the screen.
Select "Cancel share" (or "Annuler le partage").
The cancellation will be processed immediately, and the other user will be notified.