LG Voyager VX-10000

There have been times that after ending a phone call, and it is usually when I'm on my bluetooth, I will get a beep with EV DO and several bars at the top left portion of the screen. While this is on the screen I am not able to make or receive calls. It only happens on occasion and it only lasts for a few moments. It used to happen on my VX 8300 and it has happened on my Voyager a couple of times. What is the cause of this and is there anything that I can do to stop it?