Voice OTP SMS Verification

Deliver secure verification codes globally via dynamic automated phone calls.

100%

Fallback Coverage

30+

TTS Languages Support

4.8/5

Voice Quality Score

Automated Neural Text-to-Speech (TTS)

Convert text instructions into natural-sounding speech dynamically. Our voice synthesis engine supports over 30 languages with human-sounding voice profiles, allowing you to speak verification PINs or transactional updates directly to your users' phones.

Speech Synthesis Engine
// Input Text
"Hello, your Cellco verification code is 8 4 2 9 1 0. I repeat..."

Instant Failover Recovery

Never lose a signup due to carrier delays or regional SMS grid issues. Integrate Voice OTP as a dynamic fallback channel: if a text message is not delivered within 30 seconds, trigger an automated call to read the code aloud.

Incoming Call

AuthGateway

Call Active
Decline Accept
SIP Voice Trunks

High-Definition Outbound SIP Voice Gateway

Delivers crystal-clear spoken passcode calls to landlines and mobile phones with zero audio delay.

40+ Neural TTS Voices

Natural human-sounding voice synthesis in English, Arabic, Spanish, French, Hindi, and 35+ regional dialects.

Localized Caller IDs

Display familiar local geographic numbers to increase phone call answer rates up to 94% globally.

DTMF Keypress Capture

Capture recipient touch-tone inputs (e.g. "Press 1 to confirm transfer") with instant webhook callback triggers.

Developer Console

Production-Ready Voice OTP Fallback API Integration

Copy production-tested SDK snippets or test live JSON payloads directly in your environment.

curl -X POST https://api.cellco.io/v2/voice/call \
  -H "Authorization: Bearer cellco_live_key" \
  -d '{"to":"+15550123456","digits":"9182"}'
Simulated Response 200 OK (42ms) 
{
  "status": "connected",
  "call_sid": "CA_9481920",
  "duration": "12s",
  "dtmf_captured": "1"
}
< 50ms API Latency TLS 1.3 Bank-Grade Encryption 99.99% SLA Uptime Guarantee