Contractor phone service vs contractor phone answering service: the intake layer field crews actually need

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