Every visit carries its own crew. Assignments are set when the job is booked — the Workers step — and can be changed on any visit at any time.
Change who's assigned
Open the visit and click the name next to Assigned in the details panel. The teammate picker opens:
Tick the teammates who should be on this visit — a checkmark marks who's currently assigned — and untick anyone coming off it. More than one person can be assigned to the same visit.
Tip: Not sure who has room? Check the Calendar's Team Day or Team Week view first — every person's lane side by side — then assign whoever's free.
Related: See what your whole team is working on.