Android
Set Default Phone App auf Android
When you install an alternative calling app, Android does not automatically switch incoming calls to it. The system keeps using whichever app is registered as the default phone app, so incoming calls, dial pad shortcuts, and contact tap-to-call actions all route through that one app.
This setting lives in the Default apps menu, separate from notification permissions or general app info. If your new dialer never opens for incoming calls, or the old preinstalled app keeps launching instead, the default assignment has simply not been changed yet.
To fix it, go to Settings ➔ Apps ➔ Default apps ➔ Phone app and select the app you want to use for calls.
Switching the default phone app does not delete call history or contacts, since most dialer apps read from the same shared system database. Features tied to the previous app, like call recording or a custom blocking list, may only keep working while that app stays set as default.
If no option appears under Phone app, the installed app likely does not declare itself as a dialer replacement, and Android will not offer it as a choice.