An MVNO (Mobile Virtual Network Operator) is a phone provider that doesn't own the underlying network — it leases capacity from one of the big networks and sells service under its own brand.
UK examples
- giffgaff runs on O2
- VOXI runs on Vodafone
- SMARTY runs on Three
- iD Mobile runs on Three
- Tesco Mobile runs on O2
- BT Mobile runs on EE
These are all single-network MVNOs — your coverage is whatever the host network gives you.
Multi-network MVNOs
A small number of MVNOs (Fuse included) run across multiple networks. Your eSIM holds profiles for several networks and switches between them automatically based on signal strength.