"Hey, my phone just popped up with a random 'Invalid SIM' error out of nowhere. I have US Cellular. I didn't drop my phone or anything, but I can't make calls. Do you know if there's an outage, or is my SIM card just fried? I tried restarting it but it didn't help."
Before you drive 45 minutes to the nearest US Cellular store, try these fixes in order. random invalid sim message us cellular