I'm with O2. I've got GW4C LTE, but I can't make any calls nor send text-messages from my watch if my phone is not connected to internet. If I want to leave it home it needs to be on and connected to internet. More, if I send a message or make a call my GW4 gets quickly overheated and it gets into Flight Mode. I can forget about using Google Maps because it asks to connect to the smartphone. Then again, it gets overheated. Looks like I'm stuck with another contract for ma smartwatch LTE and it's completely useless (with O2 you get separate number but only for data that can be used to connect to your smartphone if you leave it home for phone-calls or sending messages. You can't use data to stream music or so). I don't know how it is with Vodafone. You're lucky that you can make phone-calls through your galaxy watch when your phone is off. I know that in the USA they've got something called "sharing number" between few devices. Also, I watched a video where some man in Germany could make phone calls, send messages and use Google Maps without any problems even when he left his phone off home.
