The unnecessary drive costs more than the missed call
In mobile mechanics, a poorly qualified request is not paid for in counter time, it is paid for in kilometres. You get there, the vehicle is on a sloped lot, the part is the wrong one, or the job needs a hoist: the morning is gone, and the customer is disappointed by a service that should not have been offered.
Your receptionist asks the questions that decide the drive. The vehicle and the symptom, of course — but also the exact location, the access, the working surface, whether the vehicle is outdoors or in a garage, and whether the spot is safe to work in. Those are the feasibility criteria in your protocol, asked before you start the truck.
She also announces what you announce: a window, not a precise arrival time, because a drive depends on traffic and on the job before it. And when a request falls outside what you do on site, she says so — the vehicle goes to a shop or gets towed, instead of committing you to a job that cannot be done there.