Need to implement custom android native dialer with advanced features call transfer and conference

Team,
I have implemented Android native dialer with a basic call feature to replace system's default dialer by setting as default app. Its working fine with intents for calling.

Now we need advanced features like call transfer and Conference call. But current app not supporting these features. If try to conference call, it delegating to system default app, and no option for call transfer.
I am new to Android (I am Java developper).
Can anyone please help me to implement android native dialer with these advanced features?