iMessage via 3G when connected to wifi?
So here's the deal. We have to use AT&T's 3G Microcell in our house because our AT&T service kind of ***** inside. Granted, we can usually get 2 intermittent bars of LTE on our iPhone 5's, it's never consistent, often reverts to 4G, and more often drops calls. Sometimes texts fail, the list goes on. When home, we obviously connect to our home wifi for data because 3G also *****, but at least calls are usually ok (for the week we've been testing). I find that when we're connected to the Microcell, text messages or in our case iMessage's don't seem to go through the same way. It seems that even if we're connected to wifi, and even if we're sending an iMessage (or text), it's going over the 3G connection. I don't recall this ever being the case. Why/how would an iMessage go through via 3G even when you're connected to a wifi?
iMac (27-inch, Late 2012), OS X Mountain Lion (10.8.2), 3.4GHz Intel Core i7, 16GB RAM