I used messages to send a text to another iPhone user and I see I got charged even though I turned off the send SMS feature. The text reply from that user got billed to me. I think the reason is both users need to be using ios 5 so it goes through iCloud. The description suggests that in the first paragraph of the description of how imessages work from the apple site but does not repeat this apparent limitation in the second paragraph suggesting you can send messages to other iPhone users without cost. Is what I am describing and assuming sound correct?