I was hoping that 6.0.1 would fix this, but it doesn't appear to have. When on wifi and I send a message from my iPhone to another on iMessage, it uses 3-4 kbs of cellular data. I thought it wasn't supposed to use any while on wifi?
Apparently iMessages prefers cellular data over WiFi. It's been this way since its inception: it is more secure over "3G" than WiFi. It will fall back to on WiFi if cellular is inadequate.
"First off, what’s surprising in the case of the iPhone is that iMessage appears to prioritize cellular data for strictly text delivery"
Just to add: I've easily sent and receive over 2,000+ iMessages this past month and have not exceeded 19MB of cellular data. And note that 19MB of data includes other stuff like web browsing and other usage.
Wow! Thank you very much. I guess that answers my question. Weird that it doesn't seem to be something that has gotten a lot of notice on the internet. I guess most people don't realize it or care. I was worried about photos and video but it seems to prefer wifi for those. Interesting. Anandtech has such indepth reviews.