Help Signal bar


Android Enthusiast
Hello guys.

I recently bought an At&t Galaxy Note on ebay. I unlocked it via IMEI code and it has been working fine for a few weeks. What I did noticed today is that when I pull out the sim card, the phone keeps showing signal bars as it had a sim card on it. I flashed the latest firmware of JB and made a wipe data/cache, but this is still shown. The phone actually has good call and 3G reception so it is not actually a problem, but I am concerned of why is this happening.