How do I tell other users/contacts my iMessage is turned off? How do I tell other users/contacts that my iMessage is turned off? I frequently turn my son's data plan off mid-month because he eats up most of our shared data.  

When I do this, however, he no longer can receive iMessages until he is connected to WiFi.  The sender doesn't usually receive a message of "not delivered" for some reason or if they do it's hours later.  Non iPhone messages are not a problem which I understand why. It is just iPhone to iPhone  messages.  It appears both parties have to turn off I-message for it to be seamless.  

Is there a feature that alerts a text sender that the recipients iMessage  is off; "please send as SMS"; besides the delayed "not delivered" notice?
As far as I know you can only do that manually. 

There are few differences between a Text Message and an iMessage. 


The most obvious an iMessage has a blue colored background and a regular Text Message has it's background green

The name of the contact/number you are sending to will turn blue or green respectively for iMessage and for a regular Text Message

After resolving the phone number of the receiver(described above), the text box will automatically say what kind of message will be send and the "Send" button will be colored blue or green respectively for iMessage and for a regular Text Message