Generations
Analog cellular systems were followed by digital voice and messaging, broader mobile data, LTE and later 5G deployments. A generation change affects more than headline speed: supported calling and equipment can also change.
Devices outlive networks
An old handset can still power on while lacking support for the current service. Compatibility should be checked against the present provider, not only against the phone’s original release material.
Brands change
Merger announcements and consumer migrations are not the same event. Corporate ownership can change while an individual account continues under a distinct brand or transition process.
Use history carefully
Historical material explains how a service arrived at its current position. It should not be used as proof that an old promotion, unlock rule or support process is still available. Each carrier guide links to current reference points.