I have a new iPhone 4s. Friends were asking, why I wasn't responding to their messages. It seems that I do not receive regular text messages from other iPhone users (the green screen - when we looked at our phones side by side).
I do seem to receive iMessages (blue screen) when comparing our phones. My phone goes back and forth between sending regular text and iMessages - and it seems like all my messages have been sent. Other iPhone users messages say they have sent, but I am not receiving them (and it seems to just be the text message with the green screen from other iPhone users.)
All of my friends have an iPhone3, and I am the only one with an iPhone 4s. How can I receive regular text messages from other iPhone users?