Android - SIM Settings
Overview
In the SIM settings, you can specify the default SIM card to be used within the Reach application.
Note: These settings will not affect your phone's system-wide SIM card settings, they will only apply within the Reach app.
Each contact has a communication line setting. You can leave this setting as default or you can choose a specific SIM card from which messages will be sent to that particular contact. For more details, you can read Edit Contact.
Changing Default SIM Settings in Reach
Go to the settings through the drawer menu.
In the settings, find the "SIM Settings" section.
In this section, there is a single field. Tap on it.
From the dropdown list, select the desired communication line. If "Line 2" is marked as "not available," it means the second SIM card is not installed.
By following these steps, you can easily manage which SIM card will be used by default for communications within the Reach app.