I have felt it since long, that phone calls should be like emails. For example, the ring should include an (optional) recorded subject of the caller (of course,

I have felt it since long, that phone calls should be like emails. For example, the ring should include an (optional) recorded subject of the caller (of course, may be heard on demand, by the receiver of the call for privacy reasons). In fact anyone not in contact list, should be required to send a brief voice subject/purpose of calling, which may be limited to 10 seconds. Also we should be able to respond by pressing a 'Not interested' button. This will take the problem of spam away.