When a caller hangs up before reaching a human — no answer, busy, voicemail, abandoned in IVR — automatically respond with an SMS. This pattern is the single highest-ROI play in service-industry telephony. Industries that adopt it consistently recover 40-70% of otherwise-lost leads.
\nA \"missed\" call is any inbound call where the desired outcome (reach a live human, complete a transaction) did not happen. Six common terminal states:
\n| State | SignalWire/LaML call status | Common cause |\n|---|---|---|\n| No answer | no-answer | All ring targets timed out |\n| Busy | busy | Destination was on another call |\n| Failed | failed | Carrier-level failure (e.g., bad number) |\n| Voicemail left | completed (call was answered by VM) | Caller hit voicemail |\n| Voicemail no-message | completed (short duration, no recording) | Caller hung up at VM beep |\n| IVR abandon | completed (short duration, no transfer) | Caller hung up in menu |
Each state may warrant a different text-back message.
\nInbound call → SWML or LaML script → call ends\n ↓\n Webhook fires on call.completed event\n ↓\n Check: did caller reach a human? did they leave a message?\n ↓\n If \"missed\" by any definition: trigger SMS within 60s\n ↓\n SMS sent from same DID the caller dialed\n ↓\n Reply tracked back to CRM thread (GHL conversation, HubSpot ticket, etc.)\nConfigure the phone number's voice URL to point at your SWML, and the status callback URL to fire on call termination:
\n@app.route(\"/call-status\", methods=[\"POST\"])\ndef call_status():\n call_status = request.form[\"CallStatus\"]\n call_sid = request.form[\"CallSid\"]\n caller = request.form[\"From\"]\n called = request.form[\"To\"]\n duration = int(request.form.get(\"CallDuration\", 0))\n answered_by = request.form.get(\"AnsweredBy\") # only set if AMD ran\n \n if is_missed_call(call_status, duration, answered_by):\n message = compose_text_back(call_status, caller)\n send_sms(from_=called, to=caller, body=message)\n log_to_crm(caller, call_status, \"Text-back sent\")\n \n return \"OK\"\n\ndef is_missed_call(status, duration, answered_by):\n if status in (\"no-answer\", \"busy\", \"failed\"):\n return True\n if status == \"completed\" and duration < 15:\n return True # IVR abandon or quick hangup\n if answered_by in (\"machine_start\", \"machine_end_beep\", \"machine_end_silence\"):\n return True # VM picked up\n return False\nPersonalize by call state. Generic \"we missed you\" copy converts worse than state-specific copy.
\n\n\n\"Hi! This is Sarah at Acme Plumbing — we just missed your call. Reply with your address and the issue, and we'll get a tech out today. Or call us back at +1 555-1234.\"
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\n\n\"Hey, sorry — we were on another call when you reached out. Reply here and we'll get back to you in 5 minutes. — Acme Plumbing\"
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\n\n\"Got your call but didn't catch a message. Text me here with what you need and I'll handle it right away. — Sarah at Acme\"
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\n\n\"Hey — we noticed you called and hung up. Anything we can help with? Text us back and we'll skip the menu. — Acme\"
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\n\n\"We're closed until 8 AM, but we got your call! Text us with the issue and we'll respond first thing. Emergency? Call +1 555-9999. — Acme\"
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Keep messages under 160 characters when possible — single SMS segment, fastest delivery, lowest cost.
\nConversion drops sharply with response delay:
\n| Response time | Recovery rate |\n|---|---|\n| < 60 seconds | 40-70% |\n| 1-5 minutes | 20-40% |\n| 5-30 minutes | 10-20% |\n| 30+ minutes | < 5% |
\nThe window collapses fast because callers move on to the next vendor. Build the webhook handler to fire SMS synchronously inside the status callback request — don't queue for later.
\nThe SMS reply must land in the same CRM thread that tracked the call. Three common patterns:
\ndef send_via_ghl(from_, to, body, location_id):\n # GHL conversations API auto-threads SMS + calls by phone number\n requests.post(\n f\"https://services.leadconnectorhq.com/conversations/messages\",\n headers={\"Authorization\": f\"Bearer {GHL_TOKEN}\", \"Version\": \"2021-04-15\"},\n json={\n \"type\": \"SMS\",\n \"contactId\": resolve_contact(to, location_id),\n \"message\": body,\n \"fromNumber\": from_,\n },\n )\nGHL automatically threads the SMS into the same conversation as the inbound call.
\nSend SMS via SignalWire, then push a Note or Activity to the CRM:
\ndef send_and_log(from_, to, body, contact_id):\n sw_response = send_sms(from_, to, body)\n hubspot.engagements.create({\n \"type\": \"SMS\",\n \"associations\": {\"contactIds\": [contact_id]},\n \"metadata\": {\"body\": body, \"direction\": \"outbound\"},\n })\nINSERT INTO call_events (call_sid, type, direction, body, created_at)\nVALUES ($1, 'sms_textback', 'outbound', $2, now());\nThen a dashboard view filters by phone number for unified conversation view.
\nIf the same caller misses multiple calls in a short window (often happens with frustrated callers re-dialing), don't text them five times.
\ndef should_send_textback(caller, called):\n recent = db.query(\"\"\"\n SELECT 1 FROM textback_log\n WHERE caller = $1 AND called = $2\n AND created_at > now() - interval '15 minutes'\n LIMIT 1\n \"\"\", caller, called)\n return not recent\nCool-down window of 15 minutes is a common default.
\nEven though the caller initiated contact (which arguably implies consent for follow-up), STOP must still work:
\n@app.route(\"/sms-inbound\", methods=[\"POST\"])\ndef sms_inbound():\n from_ = request.form[\"From\"]\n body = request.form[\"Body\"].strip().upper()\n \n if body in (\"STOP\", \"STOPALL\", \"UNSUBSCRIBE\", \"QUIT\", \"CANCEL\", \"END\"):\n db.opt_out(from_)\n send_sms(to=from_, body=\"You've been unsubscribed. Reply START to resume.\")\n return Response(\"\", mimetype=\"text/xml\")\n \n # Normal inbound handling\nTag each text-back so you can measure recovery rate:
\nCREATE TABLE textback_events (\n id UUID PRIMARY KEY,\n call_sid TEXT,\n caller TEXT,\n sent_at TIMESTAMPTZ,\n replied_at TIMESTAMPTZ,\n converted_at TIMESTAMPTZ,\n revenue NUMERIC\n);\nA \"conversion\" can be:
\nTrack all three to compute the recovery funnel.
\nInbound caller initiating contact does not by itself create marketing consent. The text-back must be transactional (responding to their inquiry) not promotional (selling a different service).
\nTransactional, allowed:
\n\n\n\"We missed your call about plumbing — what's the address?\"
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Promotional, not allowed without prior opt-in:
\n\n\n\"We missed your call! Get 20% off any service today with code AUTUMN20!\"
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Mixing the two (\"Sorry we missed you — also we have a sale!\") drifts into marketing territory. CTIA enforces this in the gray zone.
\nCombine the AI receptionist (handles the call when possible) with text-back (recovers when AI didn't reach a human or wasn't enough).
\nFlow:
\nFor callers who do leave a voicemail, transcribe it and text the transcript back to confirm receipt:
\n@app.route(\"/voicemail-recorded\", methods=[\"POST\"])\ndef voicemail_recorded():\n recording_url = request.form[\"RecordingUrl\"]\n caller = request.form[\"From\"]\n called = request.form[\"To\"]\n \n transcript = transcribe(recording_url) # AssemblyAI, Deepgram, or SW transcription\n summary = summarize(transcript)\n \n send_sms(\n from_=called,\n to=caller,\n body=f\"Got your voicemail: '{summary[:120]}'. Reply here to add details or call back at any time.\",\n )\nThis shows the caller their message was received and gives them a low-friction way to add information.
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