I purchased my LG900 Net 10 phone about a month ago along with a prepaid card worth 300 minutes and 120 service days. It worked fine until about a week or so ago when the welcome screen switched from "Home" to "Unregistered SIM". I could not make any calls, receive any calls, access the internet, or send texts. At this point, I tried contacting customer service. They advised to take the battery out while the phone was still on so that the network could update the SIM card. I did this and it worked for about 10 minutes. However, it has gone back to "Unregistered SIM" and I am right back where I started. Does anyone know of a way to fix this problem? It's incredibly frustrating to pay for a phone and then have it stop working within a month.