Understanding CallDirectory extension

Hi there,

I'm trying to create an extension for my app so that it identifies caller.

I followed https://developer.xamarin.com/guides/ios/platform_features/introduction-to-ios10/callkit/#Implementing-a-Call-Directory-Extension

and manually added my office phone number as known identity. I made sure my phone number is not already stored in my phone and try to call me but my office name is not showing, this is just an unknown caller ringing.

I tried to remove my app from my device and deploy again, it does not help.

Reading https://developer.xamarin.com/guides/ios/platform_features/introduction_to_extensions/ it looks like extensions may need to be "enabled" somewhere. How do I find how this should be done? It is written the app itself may ask the device to invoke the extension, how?