What A2P 10DLC is, who has to register (brand and campaign), what carriers expect from opt-outs, and the mistakes that hurt delivery after you register.
A practical checklist for comparing business phone providers: setup, number portability, 911, texting rules, contracts, and what 'unlimited' leaves out.
How Meta's per-message WhatsApp pricing works since July 2025: the 24-hour service window, free replies, template categories, and when WhatsApp makes sense.