I've had to switch gears on a project that I am working for because of limitation of other providers. Currently, I've landed on using an Android phone to make outbound phone calls and I have everything working. The final piece I need to to be able to terminate the calls either after a few minutes or after leaving a voice mail. Of course the user has access to the phone but hitting the button manually is not ideal. https://github.com/cjlotz/Xamarin.Plugins/tree/master/Messaging
This is code that's working fine, but I am not sure how to say after 180 seconds kill the call, or I've left a voicemail kill the call.
var phoneDialer = CrossMessaging.Current.PhoneDialer;
if (phoneDialer.CanMakePhoneCall)
{
phoneDialer.MakePhoneCall("+18888888888");
}