Car service centres earn from customers who come back every few months, not from one visit. For that to happen, the customer needs two things: booking that is easy, and knowing what is happening with the car without chasing anyone. Phone-only booking at rush hour breaks that from the first call.
A booking page where customers choose the service and time solves two problems at once: they book whenever they remember, and work spreads across the whole day instead of piling up in the morning. When slots are counted against lifts and mechanics, overbooking stops.
A history for every car is what turns a visit into a relationship. Knowing the last oil change and the mileage lets you send a reminder before the next service is due. The customer feels remembered and returns to you instead of the nearest workshop.