The failure mode
A transport operation coordinating by phone works well right up to the volume where it does not, and the collapse is sudden. Bookings taken verbally, drivers assigned by whoever is nearest the phone, jobs whose progress is known only by asking, and invoices raised from memory at the end of the week.
Duplicate invoices are the symptom everyone notices first, because a customer complains. The actual problem is that no record of a job exists between the booking and the bill.