My LG Xenon keeps saying I have no service. It has worked for a while up until now. I have taken the battery out and put it back in several times to see if I will get service, but it will not work.

Looks like you need to replace your old sim card with new one. But before you can do that you must unlock your phone first by using lg xenon unlock code for your current network. This lg unlock code is used to reset your phone network to default factory setting so you can replace your sim card.

It is likely that your SIM card needs replaced. Most service providers will give you a replacement SIM free of charge. Hope this helps!