Verizon is taking an extra step to protect its phones. CNET: The nation's largest wireless carrier said Monday that it would begin locking the phones it sells to consumers, which will prevent them from using a SIM card from another carrier. Initially, the phones will be unlocked as soon as a customer signs up and activates the service. But later in the spring, the company will begin the practice of keeping the phone locked for a period of time after the purchase -- in line with the rest of the industry. Verizon said it is doing this to deter criminals from stealing phones, often on route to retail stores or from the stores themselves.