A client can cancel his reservation only if at the end of the reservation process he has received an email containing a cancellation link.

This is why the staff member must pay attention and include a cancellation link if he wants to allow his clients to be able to cancel.

This link is very simple to add, a built-in tag must be used: %cancelation_url%. This tag will generate the cancellation link, so that when the client will receive the email instead of the string %cancelation_url% he will see the actual cancellation link.