Attach some dangling USB modem with a data SIM, or just keep a mobile router with a data SIM in your backpack, for 3G/4G/5G data connectivity over WiFi. Then, use some VoIP provider if you actually need a phone number as well.
Attach some dangling USB modem with a data SIM, or just keep a mobile router with a data SIM in your backpack, for 3G/4G/5G data connectivity over WiFi. Then, use some VoIP provider if you actually need a phone number as well.