How Onoff uses GSM

Onoff combines VoIP and GSM to give your cloud-based number the reliability of a traditional mobile line. This article explains how both technologies work together.

Two ways to make and receive calls

VoIP mode (default) Calls and messages travel over Wi-Fi or mobile data. No roaming fees, works across multiple devices.

GSM fallback When VoIP is unavailable or disabled, calls are routed through your main SIM card and mobile operator. Standard carrier rates apply, including international and roaming charges.

🔵 How to switch modes — In the Onoff app, toggle the Call via Wi-Fi/data option on or off to choose your preferred routing.

Which mode should you use?

Why Onoff numbers work like real mobile numbers

Onoff numbers are genuine mobile numbers, not app-only identifiers. They are recognised by carriers and third-party platforms, which means they work for:

• Bank and identity verifications
• Two-factor authentication
• Social media account registration
• Delivery and booking services

GSM fallback and connectivity

In areas with limited internet but strong cellular coverage, GSM fallback ensures you never miss a call. Onoff routes the call through your main operator's network automatically, with no action required on your part.

🔵 Available countries — Onoff offers real mobile numbers in France, Belgium, the United States, and others. These numbers are fully recognised by other operators and platforms.

Need help?

If you need to configure GSM fallback or check how your number is routed, contact our support team at support@onoffbusiness.com or visit the Help Center.