Twilio-Based "Missed-Call Text-Back" Developer

Project title:
Missed Call Text-Back System (Twilio-Based, Reusable for Multiple Clients)

Project description:

We're a marketing agency working with home-service businesses (plumbing, roofing, electrical, etc.) and need a developer to build a missed-call text-back system.

What it needs to do:

Detect when an incoming call goes unanswered
Automatically send an SMS to the caller within seconds
Support two-way texting (caller can reply, we can respond)
Prevent duplicate messages if the same person calls multiple times
Built on Twilio (or similar) — needs to be reusable/template-based so we can deploy it across multiple clients, not a one-off build for a single business

Nice to have:

Experience with A2P 10DLC compliance (US SMS registration requirements)
Experience building for agencies / multi-client setups (e.g. per-client subaccounts)

What we need from you:

Confirm you've built something similar before (examples/portfolio welcome)
Rough timeline and cost estimate
Any questions on scope before we lock in details

Looking to move quickly with the right developer — happy to discuss ongoing work if this goes well.