US used to have Verizon, Sprint, T-Mobile, Cingular and ATT. There was an active roaming agreement in at least California for T-Mobile and ATT so they shared coverage there, but otherwise pretty much 5 national networks before the ATT T-1000 reformed, and Sprint died.
I've seen some countries where they had three established GSM networks and then someone starts repurposinf their CDMA network for mobile handsets, but it had been built and operating for years for fixed wireless, phone lines for houses without wires.
I've seen some countries where they had three established GSM networks and then someone starts repurposinf their CDMA network for mobile handsets, but it had been built and operating for years for fixed wireless, phone lines for houses without wires.