EOS , does it call 911 if you fall etc.

Some form of wireless communications is required.

Use Emergency SOS on your Apple Watch - Apple Support

“Emergency SOS requires a cellular connection or Wi-Fi calling with an Internet connection from your Apple Watch or nearby iPhone.”

Whether you might get the call through with 911 and a cellular capable Apple Watch and with no cellular plan (if that is your question here), I do not know. There are issues with that approach, even if it does work.

Related: https://www.911.gov/calling-911/frequently-asked-questions/

This explains.

Use Fall Detection with Apple Watch - Apple Support

From the Apple Watch User Guide:

”You can use cellular models of Apple Watch Series 5, Apple Watch SE, Apple Watch Series 6, Apple Watch Series 7, Apple Watch Series 8, or Apple Watch Series 9 to make an emergency call in many locations, provided that cellular service is available. Some cellular networks may not accept an emergency call from your Apple Watch Series 5, Apple Watch SE, Apple Watch Series 6, Apple Watch Series 7, Apple Watch Series 8, or Apple Watch Series 9 if your Apple Watch isn’t activated, if it isn’t compatible with or configured to operate on a particular cellular network, or if isn’t set up for cellular service.”

This makes it sound like with no cellular service on the Apple Watch, a nearby iPhone is required.