Programmable voice(outgoing API)

I am using programmable voice(outgoing API) for my app. When I make a call to the client using this API, I get the same response status "NO ANSWER" when client did not respond to the call. And if client has no internet connection in other words data is off then also I get the same response status"NO ANSWER".

So how can I differentiate that "NO ANSWER" is received for which case (Internet is off or client did not picked the call.).