Disclosure up front: I am Abe, founder of OnCrew, which builds an AI phone answering layer for contractors. I have a bias. This post is the system design I wish I had read two years ago, written for builders and operators wiring up telephony for plumbing, HVAC, electrical, garage door, roofing, locksmith, and similar field-service shops. Pick whatever vendor you want. The architecture below holds either way. A short note on terminology first, because it trips up almost every spec doc I have seen in this space. The vocabulary problem "Contractor phone service" and "contractor phone answering service" sound like the same product. They are not. A contractor phone service is the transport and routing layer. It owns the business number, the SIP trunk or carrier integration, IVR menus, voicemail, call recording, and the rules that decide which device or queue a call rings. Twilio, RingCentral, OpenPhone, and similar products live here. They move audio. They mostly do not talk.…