I have a pantech burst phone, and it has been working well so far. but today, i went to turn it on, and it displays a "no sim inserted" thing and it says powering down, which it never actually does. so i opened it up, took out the battery and the sim, put back in the battery and the sim. and i turned it on and got the same screen. not sure what happened or what to do. thanks for any help you can offer.