There could be a number of reasons why you can’t activate your new phone on your
network; the most common one though has to do with your specific carrier.
In the United States, we have two types of network frequencies that our phones can run
on. The first is called GSM or Global System for Mobile communication and the second is called CDMA or Code Division Multiple Access.
Without boring you with the specifics, with GSM devices, your phone number is linked to the SIM card. So when switching devices, all you have to do is pop the SIM card into a new phone and you’re all set!
CDMA on the other hand is handset-based. That means even though your phone has a
physical SIM card; your phone number is linked to a specific device. Therefore, the only
way to activate your new phone is to get in touch with your carrier so they can
de-activate your old device and activate the new one