A:Answer As it is marked as GPS + Cellular, it has the necessary hardware to have its own cellphone line. It just means you don't need to carry your iPhone with you to make a call via this watch. I have a GPS only Apple Watch and when the iPhone is nearby and connected via Wifi?Bluetooth I can answer the call via my watch. Kinda sorta like Dick Tracy's 2-Way wrist TV. Well...kinda. Not sorta. LOL!
Either version of this watch will serve you well. So far, I don't really miss not having a watch that is also a standalone cell phone as I have my iPhone with me most of the day. And yes. The extra phone line for the watch will cost your whatever you carrier charges for another line.