I am on metered text plan with AT&T (Nation 450 + 200 Text Message add-on) and this works pretty well for me since I'm not a heavy user. However, this month there was a flurry of texts which actually pushed me close to my limit. I noticed that not all my messages are showing up on my AT&T account so I presume these were sent via WiFi/Messages. Does anyone know if receiving texts work the same way? For instance, if my sister is on WiFi and is using an iPhone with Messages enabled are those free to me (non-SMS) too? Presuming the above is true is there any way to tell which are (Messages vs. SMS)? I presume not since my texts are either blue or green but theirs are always gray. Thanks!