If you can, try to clean the gold colored contacts in the SIM slot. Be very careful not to bend the pins or force anything. Use either rubbing alcohol with a Q-Tip or gently rub with a clean pencil eraser.
Worst case, ask your carrier for a replacement SIM card.
I recently bought a used (yet mint condition, tested and guaranteed fully functional) Samsung C414 flip phone to replace my failing Samsung A167 flip phone I use as a company emergency service line. They're both GSM phones, unlocked. My network is Airvoice Wireless.
My problem: After inserting my SIM card into the newer C414, it recognizes the network for just a second or two, then shows "Unregistered SIM" on the screen, and I'm unable to make or receive calls. The phone is perfectly able to view contacts and messages saved to the sim and even acknowledges the phone number in settings, but the service is essentially unusable.
I've did some research on my own and asked around but haven't really gotten a straight answer. The network is fine on the old phone but useless on the newer one. Is the SIM technology different? I need to figure this out before the old phone fails completely.
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