A simple app to let you individually switch the primary SIM for data, voice, and SMS on your device without any special permissions.
In theory, SIMSwitcher should work on any device running Android 7.0 or later with multiple SIMs active. It makes use of a leftover Activity inside the System Settings app that can be launched by normal apps.
There is a possibility that some manufacturers will have removed or restricted access to this Activity, so SIMSwitcher may not work on every device. However, it does work on Samsung One UI 6.1 and likely other versions of One UI.