When receiving calls, instead of the actual caller ID, the Secondary number appears as the call source

This can occur on Android devices, and is due to several reasons:

Make sure that the application has permission to run in the background (the permission does not consume much battery resources or data) and that it is not submitted for battery optimization.
Make sure that the application has permission to use background data.
The application must be allowed to display all types of notifications.
Make sure that your device has an internet connection.
Check the device contact list to see if the Secondary number was added as a contact, if so, delete the number from the phonebook.
If outgoing calls also appear when calling the Secondary number instead of the destination number – make sure to grant the app permission to access the device phonebook.
If the problem occurs for incoming calls on Xiaomi devices, make sure to give the application permission to display notifications, unique to this type of device.

If you have checked all the above settings, and have not found the problem, please contact us at num2@cellact.com.

Check and pass us the following details:

Does the Num2 app receive SMS messages?
Do you receive SMS messages to the Primary SIM number (of the device on which the app is installed)?