Phone acts like it is in flight mode but the airplane icon is not showing. The only way I can get it to work is to put it...

HI Jayeff; It performs as though it is in flight mode but it is not activated. I have to activate flight mode, then I attempt to make a call. When I do, it ask if I want to exit flight mode. I press "yes" and then it works for a while until it changes back on its own. When it is in flight mode, there is an airplane icon on the display screen. When this problem occurs there is no icon to indicate it being in flight mode, though it acts as though it is. The only way I know it has changed is when I try to make a call. Something seems to be triggering it but I have not figured out what it could be. Anyway, thanks for your help.