I have switched to iphone 4 in July 2010. International message to China mobile had been fine until Oct 2nd. Since Oct 2nd, I can send text message to China Mobile but they only can receive message in English but Chinese. Even worse since today (Oct 11th), they can't receive any messages (neither English nor Chinese). When users send messages to my iphone 4, they always get "We have received testing message" as an automatic reply. I have called couple of friends located in different cities in US. They all have exact same problem. Is this caused by AT&T or by Apple iPhone 4 firmware? Please help!!!!