Kindly note that if ticket is not booked in the system then it can only be deleted. In summary "booked" request can be cancelled and "Approved" request can only be deleted. So in order to instruct Travel desk to not book your request you have to delete the request.

Follow the steps here: 

- Go to the trip you wish to delete
- Click on Edit icon on top right corner
- Delete segments, you wish not to pursue. Delete icon is right corner of all segment card.
- You may delete all segments if your entire trip plan is cancelled
- Once deleted all segments, click on "Continue" 
- Click "Submit" on next page

Trip request would go to appropriate approval and then reach travel desk stating change in trip request.