How to Make Phone Calls with Bitcoin Lightning
Real calls to real phone numbers — from your browser, with no SIM card, no phone plan, and no account. Or automate them via API. Pay per minute with Bitcoin Lightning.
Live calls
Two-way voice conversation — browser to any phone number. Works like a regular call but paid with Lightning. Needs a microphone.
Automated calls
Deliver a pre-recorded message or text-to-speech when the recipient picks up. No microphone needed — works via API or browser.
AI calls
Send an AI voice agent to make the call for you. Describe the task, choose how many minutes to deposit, and get back a transcript with a structured summary. Unused time is refunded.
For Humans
Every option for calling a real phone number requires an account, a plan, or a SIM card — except this one.
Traveling abroad
You land in a new country and need to call a hotel, taxi, or local business. Your carrier charges $3/minute for roaming. With Sats4AI, you call from your laptop on hotel WiFi for a few sats per minute — no roaming plan needed.
Phone is dead or broken
You're at a computer and need to reach someone right now. Open the page, dial the number, pay the invoice. No app to install, no account to create, no SIM card required.
Privacy — no caller ID
Calls are placed from a service number, not your personal number. No caller ID tied to your identity, no account linked to your email or name. Pay with Lightning and leave no trace. Need to send a message too? Chain with SMS.
No international plan
Instead of buying an expensive international add-on or a prepaid SIM, pay a few sats and call directly. Works from 200+ countries to 200+ countries. Unused minutes are refunded automatically.
For Agents
Traditional telecom APIs require contracts, monthly fees, account approval, and compliance paperwork. With L402, you send an HTTP request, pay the invoice, and the call is placed. No vendor lock-in, no recurring charges, no minimum spend.
Server alerting
Your monitoring system detects downtime. It calls the API, pays 200 sats, and your on-call engineer's phone rings 3 seconds later. No telecom account needed.
Appointment reminders
Generate a reminder in any language using TTS, then pass the audio URL to the call API. Each reminder costs a few sats — no monthly contract.
AI customer service loop
Transcribe a voicemail, generate an AI response, convert to speech, then call the person back with the answer. Fully automated, paid in sats per step.
Multi-channel outreach
Send an SMS first, then follow up with a phone call if no response. Both services use L402 — no separate accounts or contracts required.
L402 automated call — 3 steps:
# Step 1 — send without auth, get invoice
curl -s -X POST https://sats4ai.com/api/l402/place-call \
-H "Content-Type: application/json" \
-d '{
"phone_number": "+14155550199",
"message": "Your server is down. Please check immediately."
}'
# → 402 Payment Required + Lightning invoice
# Step 2 — pay the invoice (any Lightning wallet)
# Step 3 — resend with payment proof
curl -X POST https://sats4ai.com/api/l402/place-call \
-H "Content-Type: application/json" \
-H "Authorization: L402 <token>:<preimage>" \
-d '{ ... same body ... }'
# → { "status": "queued", "callId": "..." }How to Make a Live Call
Open the call page
Select the Live Call tab. No login required.
Choose minutes and enter the number
Select how many minutes you want. The price in sats updates live as you adjust — you see exactly what you'll pay.
Pay the Lightning invoice
Click Call. A QR code appears. Scan with any Lightning wallet — Phoenix, Alby, Zeus, Wallet of Satoshi, or a WebLN browser wallet.
Talk through your browser
The call connects. Speak through your microphone — like a video call, but audio-only to a real phone number. A countdown shows remaining time.
Hang up and get a refund if early
Hang up before your paid time runs out and unused minutes are refunded automatically.
AI Calls — Let an Agent Handle It
Sometimes you don't want to make the call yourself. You want to book a table, cancel a subscription, or check if a store has something in stock — but you don't want to sit on hold for 20 minutes to find out. AI Call sends a voice agent to do it for you.
You describe the task in plain language, pick a phone number, choose how many minutes to deposit, and pay with Lightning. The AI agent calls the number, navigates the conversation — answering questions, handling objections, following up on details — and brings back a full transcript with a structured summary of what happened. If the line is busy or goes to voicemail, the agent retries automatically at no extra cost. Unused time is refunded automatically.
Deposit billing
You pay for N minutes upfront at a per-minute rate (telephony + AI agent cost). After the call ends, actual duration is measured server-side. Unused sats are refunded automatically to your Lightning address.
Example: deposit 5 minutes at 80 sats/min = 400 sats. Call lasts 2.5 minutes = 200 sats used, 200 sats refunded.
Describe your task
Write what you want the agent to do, in plain language. "Book a table for 2 at 7pm Saturday at Chez Michel" — be as specific as you need. If key details are missing (date, time, party size), the system asks clarifying questions before making the call.
Enter the phone number and choose minutes
Pick how many minutes to deposit for (1-30). The price in sats adjusts per minute based on destination. Unused time is refunded.
Pay and let the agent work
Pay the Lightning invoice. The AI agent places the call, handles the conversation, and retries automatically if the line is busy or goes to voicemail (up to 3 attempts, included in your payment).
Get your results
You receive a full transcript of the conversation plus a structured analysis — what was agreed, next steps, and whether the task was completed. If it wasn’t, you get the full context to adjust and try again.
Skip the hold music
Need to book a doctor's appointment, confirm a reservation, or ask a business a quick question? Send the AI agent instead of waiting on hold yourself. You get the answer in a transcript — no 15-minute hold required.
Cancel subscriptions painlessly
Companies that make cancellation deliberately difficult are betting on your patience running out. The AI agent doesn't get frustrated, doesn't give up, and follows your instructions precisely.
Call in another language
The AI agent supports 7 languages. Need to call a restaurant in Tokyo or a hotel in Barcelona? Describe your task in English and the agent handles the conversation in the local language, then summarizes the results back in English.
Privacy by default
The agent uses "Satoshi" as its name — no personal information is shared with whoever picks up. Combined with Lightning payment and no account requirement, there's no link between you and the call.
Three ways to use AI Call
ai_call tool from any MCP-compatible agent. The system validates your task before calling — if critical details are missing, it asks clarifying questions. On failure, the full transcript is returned so the agent can adjust and retry.POST /api/l402/ai-call with the standard L402 flow. Same 3-step pattern as all other endpoints — request, pay, resend with proof. Includes push-back for incomplete tasks and auto-retry on busy/voicemail.Featured by Blockspace
Blockspace published a step-by-step tutorial showing how to give an AI agent a Bitcoin wallet and have it pay to place a phone call — in three commands. The entire demo uses this endpoint.
How it compares
| Sats4AI | VoIP apps | Roaming | |
|---|---|---|---|
| Intl. rate | ~50–300 sats/min | $0.01–0.25/min + credits | $1–3+/min |
| Signup | None | Account + verification | Already enrolled |
| Payment | Bitcoin Lightning | Credit card | Billed to plan |
| Recurring fees | None — pay per use | Credits expire / subscription | Monthly plan |
| Privacy | No personal data | Full identity | Full identity |
| Install | None (browser) | App required | Phone required |
| Refunds | Unused time auto-refunded | No | No |
Three ways to automate calls
No contracts, no API keys, no monthly minimums. See L402 API & MCP docs.
Combine with other tools
Generate a professional voice message in any language using TTS, then deliver it via automated call. Perfect for multilingual appointment reminders.
Clone a voice once, then generate personalized messages in that voice and deliver them as automated calls — personalized outreach at scale.
Transcribe a voicemail, generate an AI response, convert to speech, then call the person back with the answer. Fully automated customer service loop.
Send a text first, then follow up with a phone call if no response. Multi-channel outreach with no separate accounts or telecom contracts.
Make a Call — No Signup Required
From landing on the page to your first call: under 60 seconds. Open the page, dial, pay, talk.