I run 6 businesses. Each one needs its own phone number, its own voicemail, its own AI receptionist. If I used a hosted VoIP provider for all of them, I would be paying $150 to $300 a month just for phone lines and auto-attendants.
Instead I built the whole thing on one VPS with Asterisk, VoIP.ms, and AI agents.
The Architecture
VoIP.ms — SIP trunk provider. I have 6 DIDs (phone numbers) in the 832 area code, all on flat rate billing through the Dallas POP. Total cost: about $6/month for the DIDs plus usage.
Asterisk — Open source PBX running on my VPS (lb-telecom-01). PJSIP trunk registered to VoIP.ms. Each DID routes to a different dialplan context based on the business.
AI Agents — Each business has its own AI receptionist. When a call comes in, Asterisk sends the audio through a pipeline: Whisper for speech-to-text, Claude for intent classification and response generation, OpenAI TTS for text-to-speech. The caller talks to an AI that knows about that specific business.
The DID Routing
832-XXX-1315 → Load Bearing Capital (real estate)
832-XXX-1316 → Load Bearing Demo (demolition)
832-XXX-1317 → Quiet Hours Valet (valet trash)
832-XXX-1318 → Luchin Credit Repair
832-XXX-1319 → Petroleum Noir (mineral rights)
832-XXX-1321 → Load Bearing Detailing (steel)
Each number hits a different AGI script that loads the right system prompt, greeting, and business context.
Cost Comparison
Hosted solution (RingCentral, Grasshopper, etc.): $25 to $50 per line per month = $150 to $300/month
My setup: $6/month DIDs + $20/month VPS + per-minute AI costs (under $0.03/min) = roughly $30 to $40/month total
Annual savings: $1,300 to $3,100
The Hard Part
Asterisk configuration is not fun. The dialplan syntax is archaic. PJSIP debugging will make you question your life choices. But once it works, it works. And you own every piece of it.
If you are running multiple brands and paying per-seat for phone service, consider building your own. The upfront pain pays dividends.
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