My mom can't send me iMessages and she has iPhone4 and I know iMessage works on my iPhone 5 The button "Use your apple ID ..... " doesn't work on her phone on iMessages settings, but she entered her phone number properly to be used for iMessages. I tried turning on and off the iMessages. Still doesn't work and she is sending me SMS regular instead of iMessage iPhone to iPhone. I even managed to send her iMessage from Macbook to her iPhone 4 using Message app for Macbook, but not from iPhone 5 (I have iPhone 5). But Apple, (please) this is the BASIC BASIC function of a telephone, why can't you fix this......I love Apple and all but things like this make me freaking jump out of my skin....the simplest basic stuff :)
I'm with you, this pisses me off. This small explanation may help:

iMessages on an iPhone has two ways of sending a text.

iMessage


  This is the blue colored bubbles. It requires data to be turned on to
  send and receive messages. It goes through apple servers. This can be
  sent between macs, iPads, iPods, and iPhones.


SMS


  This is the green colored bubbles. It does not require data and it
  goes through cell towers from your carrier. This can only be sent to
  phones, including android phones, those old Nokia phones, and anything
  that can receive text messages. It does not send to a mac, iPod, and iPad without cellular


On an iPhone you can have both enabled, or just SMS. You cannot disable SMS.