To delete a request, tap the menu icon (3 dots) at the right side of the request and choose 'Delete request'. Please note that your credit will not be refunded. The reason for this is that another member might already be putting effort into retrieving the loads to answer your request. As you can imagine, it would lead to frustration if the request is deleted by the time they get back to the app to enter the loads for you.
Please note that there is no need to delete requests if they are not getting answered. Unanswered requests will be refunded automatically after the flight has departed. Requests will not be answered quicker if you delete and re-post them, as they would come up at the same position in the list of unanswered requests.