https://en.wikipedia.org/wiki/LoRa (Long Range)

It's a low power, large range connection technology, working a bit like a mesh network. It can achieve data rates between 0.3 kbit/s and 27 kbit/s and enables geolocation services. According to the LoRa Development Portal, the range provided by LoRa can be up to 3 miles (4.8 km) in urban areas, and up to 10 miles (16 km) or more in rural areas (line of sight).

As soon as your LoRa-Device is in range of another LoRa-Device, it will probably be able to phone home.