Occasionally when I call someone the iPhone 4 will just hang on "calling moblie" for example. I hear no ringing, seems like the phone has stalled on the calling screen as if trying to make a connection. I can wait and eventually will hear it ringing on the other end or press "End Call". If I do press "End Call" that will also hang for a few seconds before ending call. The next call will go through normally. Has anyone else experienced this scenario? Btw, this will happen regardless of reception.