AI Voice Agent Developer — Twilio + OpenAI Realtime API + Authorize.net (Service/Delivery Business)

Title: AI Voice Agent Developer — Twilio + OpenAI Realtime API + Authorize.net (Service/Delivery Business) Category: AI Voice Agents / Twilio Development / Backend Integration Job Description: We run a service business (heating oil delivery, service calls, and free estimates) that currently handles all inbound calls manually — taking orders, scheduling, and processing payments by hand, logging everything into Google Docs. We want to build a self-hosted AI voice agent to automate this, and we're looking for a developer to build it with us. What we have already: 90+ phone numbers on Twilio, plus 2 landlines on Optimum Online, currently all forwarded to Grasshopper Authorize.net account already integrated on our website (API Login ID / Transaction Key available) Two separate websites/platforms for heating oil delivery — one for same-day delivery (higher price), one for scheduled delivery (lower price) — each with its own pricing Google Docs currently used for logging orders, estimates, and service calls What we want built: What we want built: Route Twilio numbers away from Grasshopper to a custom voice agent server (Twilio Media Streams + a realtime AI model — we're leaning toward OpenAI's Realtime API) Call flow that can identify caller intent: heating oil order, free estimate, or service call For estimates and service calls: schedule appointments by checking calendar availability — no payment involved on these calls For heating oil orders only: determine same-day vs. scheduled delivery, pull the correct price from the matching platform/pricing table, quote the total, and confirm quantity before payment Self-service "block myself out" capability — a simple way for us (owner/dispatcher) to mark ourselves unavailable when overbooked, so the AI automatically stops offering same-day/next-day slots (for both estimates/service calls and oil delivery) and either pushes callers to the next open slot or takes a callback request instead. Needs to be something we can toggle quickly (a shared calendar block, a simple dashboard, or even a phone/text command) — not something requiring a developer each time. Phone payment capture — for heating oil orders only — via DTMF keypad entry for card number/expiry/CVV (never passed through the AI model), submitted to Authorize.net for charge, using the price from whichever of the two platforms (same-day or scheduled) matches the order Automatic logging of every completed call (order/estimate/service booking) to Google Sheets (preferred over Docs for structure), including a fallback "transfer to human" option Handle 2 Optimum Online numbers via call forwarding into the Twilio system Important: We specifically do NOT want a per-minute AI platform (Retell, Vapi, Bland, etc.) — we want to own the code and infrastructure directly, paying only Twilio and the AI model provider for usage. We have a written architecture/build guide already (happy to share on request) covering the full phase-by-phase plan — you'd be implementing against it, not starting from a blank page. Ideal experience: Twilio Programmable Voice + Media Streams (not just SMS) Direct integration with a realtime voice AI model (OpenAI Realtime API or similar) — not just wrapping a no-code platform Authorize.net API integration, ideally with DTMF/PCI-aware payment flows Google Sheets/Docs and Google Calendar API for logging and availability control Comfortable handing off clean, documented code we can maintain going forward Engagement structure: We'd like to start with a fixed-price proof-of-concept phase: one Twilio number, basic oil order flow (intent → correct price from same-day or scheduled platform → log to Sheet, no payment yet). If that goes well, we'll extend the same contract to cover payment integration, scheduling with overbooking controls, and full rollout across our numbers. To apply, please include: Relevant past projects (especially Twilio voice + AI, and any payment-over-phone or calendar-aware booking work) Your proposed approach/timeline for the proof-of-concept phase Your rate (hourly or fixed-price estimate for POC phase)