I know this is an old thread, but I just got my f90bt and am having a very similar problem. For the most part i believe I see the end call button, there was one time that I didn't, but i've only tried using my bluetooth like 4 times, and 2 of the times, after I hang up a call, then there is no sound anymore? has anybody figured out the reason for this, does anybody think the mute/video watching bypass, could be the problem? thanks