Hologram SIMs are set up to permanently roam on carrier partners and hold the credentials necessary to access 550+ cellular networks in 190+ countries worldwide. The choice to roam and connect to a network is largely driven by the cellular modem and firmware, which controls when and how devices connect.
Traditionally, a modem will scan all available networks and connect to the one that provides the strongest connection. Network availability depends on the bands your device can access, its geographical location, tower traffic, and a few other smaller factors. Ultimately, this is determined by your device's firmware. We recommend contacting your manufacturer or visiting our general firmware advice guide.
Hologram's Hyper SIMs with automatic fallback can give you access to additional networks by providing two fully independent connectivity profiles, each providing connectivity to 400+ global networks. In the event of an outage, your SIM will seamlessly transition mobile cores, minimizing downtime for your devices.