smbu2000 on 14 September 2012
Isn't that just related to the network the carrier uses? In this case CDMA.
In Japan there are two carriers who offer the iPhone; Softbank (GSM) and starting with the iPhone 4S, KDDI (CDMA). On KDDI this same limitation is in place, you can only use one or the other. With Softbank you can use both. This is not just related to the iPhone 5.
Just earlier I was talking to my girlfriend on the phone and while we were talking I sent an imessage to her iPad using my iPhone 4 to do both.
starcraft: "I and every PS3 fanboy alive are waiting for Versus more than FFXIII.
Me since the games were revealed, the fanboys since E3." 
Skeeuk: "playstation 3 is the ultimate in gaming acceleration"
