-I installed smart dimmer switches (HS220) in a barn about 250 feet away from my house

-When I installed them, I had Wi-Fi at the barn. I used the same network name & password as the house.

-I have since disconnected the Wi-Fi at the barn...BUT the switches still work?? I can control the switches from my phone in the house.

Can somebody explain how this is happening? Do you ONLY need Wi-Fi when setting up the switch, then I can move it to a remote location? How am I still able to communicate with the switch?

Thanks