Each Mover has a default position which is set in Settings > View/Edit Staff > Movers
If you want to change the position of a mover on a particular job, you can do so in the job page after assigning a mover by clicking the three dots to the right of the mover name
Then you can select a different position for that job
If you then send a text to a mover to notify them that they've been assigned to a job, they'll be able to see what position they've been assigned.
You can also do the same thing when assigning from the dispatch calendar!