Grey bubble notifying me of a response text is gone. How can I it back?

[iMore Question]

Grey bubble notifying me of a response text is gone.

When I send a text to someone using my 4s, I used to be able to see that they were responding to my text but this grey bubble no longer appears. Can I get it back?

 

[John Yester]

Re: Grey bubble notifying me of a response text is gone.

Turn iMessage back on. As that feature is only available there. SMS will not work that way.