Deliver one-time passwords via automated phone calls with automatic language detection across 220+ countries. Net2APP Voice OTP integrates with Asterisk AMI for reliable call origination, supports alphanumeric OTPs (A-Z, 0-9), and includes built-in 3-retry logic with full call logging.
220+
Countries Supported
Automatic MCC language detection
A-Z,0-9
Alphanumeric OTPs
Full letter + digit support
3x
Retry Logic
Automatic call retry on failure
Asterisk
AMI Integration
Reliable call origination
End-to-end Voice OTP delivery flow — from API request to phone call
Your application sends an HTTP POST request with the phone number and OTP value to the Net2APP Voice OTP API endpoint.
The system extracts the MCC (Mobile Country Code) from the destination number, maps it to the local language from a 220+ country database.
An audio playlist is dynamically built: greeting audio in the detected language, followed by individual audio clips for each character of the OTP (digits and letters).
Asterisk AMI originates the call to the destination number. On no-answer or failure, the system retries up to 3 times with configurable intervals.
Enterprise-grade Voice OTP infrastructure for global authentication
Automatic country-to-language mapping using a database of 220+ Mobile Country Codes. Supports local language voice greetings for better user comprehension.
Full support for A-Z letters and 0-9 digits. Each character has a pre-recorded audio file. The system dynamically builds the playback sequence for any OTP value.
Deep integration with Asterisk Manager Interface for reliable call origination. Supports SIP trunking, call progress detection, and call detail recording.
Automatic retry on busy signals, no-answer, or failed calls. Configurable retry count, interval, and timeout settings per Voice OTP request.
Full call logs with status, duration, retry count, and timestamps. Real-time Voice OTP call monitoring via the Net2APP dashboard.
Simple HTTP API for Voice OTP integration. Trigger calls, check status, configure SIP settings, and receive webhook callbacks for delivery events.
Connect your own SIP trunk or use Net2APP's built-in SIP configuration. Configure multiple SIP providers with failover for high availability.
Upload custom greeting audio files in multiple languages. Per-language greetings can be configured from the super admin panel.
Each tenant has isolated Voice OTP configuration, call logs, and audio files. PostgreSQL schema-based data separation ensures complete privacy.
Where Voice OTP delivers the most value
Deliver OTPs for user login, account registration, and password reset flows. Voice OTP provides a reliable fallback when SMS delivery fails or is delayed.
Verify high-value financial transactions, wire transfers, and payment approvals with a phone call that reads the verification code aloud.
Help users recover access to their accounts with voice-based identity verification. Works even when SMS is unavailable or the user has changed their SIM card.
Add an extra layer of security to your applications with voice-based 2FA. Users receive OTPs via phone call as a second authentication factor.
Voice OTP serves users with visual impairments or reading difficulties who may struggle with text-based OTP delivery methods like SMS or email.
For banking, government, and healthcare applications where SMS-based OTP is considered less secure due to SIM-swap attacks and SS7 vulnerabilities.
Everything you need to know about Voice OTP service
Voice OTP delivers the one-time password via an automated phone call rather than an SMS text message. Voice OTP is useful when SMS delivery is unreliable (e.g., in regions with poor SMS infrastructure), for accessibility purposes (users with visual impairments), or as a security measure against SIM-swap attacks and SS7 vulnerabilities that can intercept SMS messages.
Net2APP Voice OTP extracts the MCC (Mobile Country Code) from the destination phone number's country code prefix. It then maps this MCC to the most common language for that country using a database of 220+ countries. For example, a Bangladeshi number (+880) will receive the OTP in Bengali, while an Indian number (+91) will receive it in Hindi or English based on configuration.
Yes. Net2APP Voice OTP supports custom SIP trunk configuration. You can connect your own SIP provider for call origination. The system supports multiple SIP providers with failover routing for high availability. SIP settings are configurable from the Voice OTP SIP configuration panel.
Net2APP Voice OTP includes automatic retry logic. If a call is not answered, the line is busy, or the call fails, the system will automatically retry up to 3 times with configurable intervals between attempts. The retry count and interval can be customized per request.
Net2APP provides a RESTful HTTP API for Voice OTP integration. You send a POST request with the destination phone number and OTP value. The API authenticates using API keys with optional IP whitelisting. Integration guides and code examples are available in the documentation.
Voice OTP is generally considered more secure than SMS OTP because it is not vulnerable to SS7 signaling attacks or SIM-swap attacks that can intercept SMS messages. Voice-based delivery adds an additional layer of security for high-value transactions and sensitive authentication flows.
No setup fees, no hidden fees. Deploy your Voice OTP service with Asterisk AMI integration, 220+ country support, and alphanumeric OTP delivery.
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