For dual-SIM users, NumBuster offers two options: automatically sending SMS from a single primary phone number or prompting for a SIM card selection before each message is sent.

1. From the NumBuster home screen, go to Settings.
2. Select Calls and Widgets.
3. Tap Phone Number for Calls. In the window that appears, select one of the following options:
   • Always ask (The app will prompt you to choose a SIM card every time).
   • One of your phone numbers (This specific number will be used automatically for all outgoing SMS).