Incoming Call when On the Phone

[teachrqs]

So after about a month of dealing with it I finally broke down and called Verizon and they were no help. When I am talking on the phone and someone calls me, the phone actually rings like I am not on the phone. I can't hear the current call until I ignore the incoming call and if I answer the call, the other person doesn't even know I clicked over. I've gone though just about every setting on the phone to no avail. I finally just put my phone on vibrate and that works but I would like to have it actually ring. Please Help!