Just found something odd with S2. I always text using my Google Voice #, with S2, in GV-->settings-->Sync and Notifications-->Notifications-->Receive text message-->I had "Also via the message app" checked, now, I assumed that sms received with GV# via the stock app is a copy of the original that still comes from GV network, not ATT. BUT, after receiving several sms this morning and went to ATT website to check the data usage, lo and behold, the sms come to my GV # showed up in ATT and ate up 6 out of my 200 $5 plan. I went to check the stock app settings, there's this ATT message center number, so I guess whenever receive sms in the stock app, it is counted toward your ATT sms usage even though they were sent to the Google Voice #. For those on limited SMS plan with ATT, make sure your setting in GV is set to "Only via the Google Voice App" under Sync & Notification!