Do you have a paid Plus or Pro subscription? If so, canceling is free.
If you have a free Start subscription, canceling 24 hours before the start of the ride or earlier will not incur any cancellation fees. If you cancel within 24 hours before the start of the ride, you will be charged 10 euros cancellation fee per reserved day.
Cancellation is only possible until the start time of the ride. Once the ride has started, you can only end it; the cancellation is no longer possible.
The right of withdrawal does not apply to reserved rides, but the above conditions apply.