By default, Freshservice doesn't allow requesters to set the priority of a ticket. However, administrators can enable this option by following the below steps,

  1. Go to Admin > Service Management > Service Desk Settings > Field Manager.
  2. Click on Ticket Fields.
  3. Under the Ticket Forms tab, scroll down to find the Priority field.
  4. Click on the Pencil icon next to the Priority field to edit its properties.
  5. Under the Behavior for Requesters section, check the box for Requester can edit option.
  6. Click Done and Save and Confirm the changes.
    Enabling the requester to change the ticket priority.

Now, requesters should be able to change the priority of a ticket from their end.