It means that if your operator's network is not available, you can switch to other operators' networks.
Mobile operators Vodafone, Kyivstar and lifecell, Derzhspetszviazok, Ministry of Digital Transformation, and NCEC launched testing of national roaming.
You can connect to the network of another operator using the following algorithm:
disable auto-network selection: on Android: Settings - Mobile network (or Connection) - Operator and on iOS: Settings - Cellular data - Network selection,
find and select an available network: Vodafone UA, UA-KYIVSTAR or LIFECELL,
if you are unable to register, try again or select another network,
check the possibility of an outgoing call, SMS.
The State Service advises trying to return (connect) to your operator's network once a day - manually or by enabling auto-selection of the network.
Tariffing is according to the tariff plan of your operator.
As you know, in Ukraine, phone calls from the Ukrainian SIM cards to Russia are limited.