I cant get a signal on my LG 1400

LG1400. I bought it (used) about 3 days ago for about 162 bucks. And it was fine for the first 10 minutes and I was able to Replinish minutes and buy a ringtone and a wallpaper but the next day I couldnt get a signal at all. I tried everything I could possibly think of and its no use. I have it on pay as u go aswell. Any help would be excellent. Thanks.