You can set exactly which services each employee performs. That way, when you make an appointment you only see the services that fit the person you picked.
Step 1 — Open the employee
On the "Staff" screen, tap the employee you want.
Step 2 — Go to the available services
Tap the "Available services" row (the number in brackets shows how many services they have right now). This opens "Select available services".
Step 3 — Tick the services
Tick the services the employee performs and untick the ones that don't apply to them.
Step 4 — Save
Tap "Save". ✅
Optional: if the employee's services are synced with the online booking page, the change shows up there automatically as well.