Several times since I got my 4S (probably 5 or 6 times) when I call someone, I will be muted on their end, but the mute icon won't be highlighted on my screen. For example, earlier today I called Home Depot to rent a nail gun. The guy at the rental desk picked up and said "Home Depot rental, blah blah blah". I then started to tell him I needed to rent a nail gun when I hear him say "Hello?" I start talking again but hear him again say "Hello? Hello?" then he hangs up. During the "conversation" I looked down at my phone several times to make sure I hadn't inadvertently tapped the mute button, but it was dark just like all the other buttons. Like I said, this has probably happened 5 or 6 times since I got mine on the 19th. Has anyone else had any issues with this?