You can archive old passengers in DispatchBot to stop them from appearing from your passenger list for new trips.  This is useful for passengers that have not traveled with you for a long time or if they were a 1 time transport.

From the Scheduler page go to More > Passengers

Find the passenger you would like to archive by typing their name in the search box then clicking search.  You can also filter by a specific account by selecting that account from the drop down menu.  Once you've located the passenger, click on their name.

Click on the Archive button to archive the passenger.  This will remove them from the search and they will not be available for future trips.  The passenger information will still be available for any existing trips.