The problem with a ringing phone
A repair shop's phone rings while everyone's hands are dirty. Calls get missed, and a missed call is usually a booking that went to whoever answered first.
Jessica answers. She can find the next available appointment slot, create an appointment request, look up the status of a work order, and pull up every work order attached to the number that's calling. When a call is outside what she should handle, she transfers it to a person instead of improvising.
Wired into the shop, not just the phone
Jessica isn't a chatbot with a phone number attached. Everything she answers goes through the same data the shop already runs on, the real calendar and the real work orders, so a caller gets an actual answer instead of a promise that somebody will call them back.
The number they're calling from does most of the work. It identifies the customer before they've said their name, so she can pull up their vehicle and every work order attached to it without making anyone recite a VIN down the phone.
It also keeps the two halves honest. An appointment she takes is an appointment the shop sees, in the same place as the ones booked at the counter. There is no second calendar to reconcile at the end of the day.