These major cellular carriers support Wi-Fi calling.

• Verizon
• ATT Mobility
• T-Mobile

Note: Cellular carrier use of Wi-Fi calling while roaming in building or between floors is not just dependent on Wi-Fi coverage but the cellular carrier technology to maintain calls as your devices jumps from one Wi-Fi AP to the other. The same is true for Wi-Fi AP to a cellular tower. Your calling experience will vary.