My phone says I have no bars and has a red cross near it. What could the problem be?

[AC Question]

My phone says i have no bars and has a red cross near it

Well I've tried lots of different Sims but I can't call myself and no one can call me.My phone acts like it doesn't even have a sim , I have a LG Optimus please help.

 

[B. Diddy]

Re: My phone says i have no bars and has a red cross near it

Welcome to Android Central! Which Optimus? Are you certain it's compatible with your carrier's network bands? Have you ever been able to use the phone?