Does the apple watch SE need a other line?

Hi; by my understanding, you’re asking if the Apple Watch SE needs a cellular line. I’m happy to help with this. If you buy a cellular model, yes, the Watch itself will need its own cellular line. Most cellular providers offer specific lines tailored just for smart watches for a fraction of the price. If you get the GPS model, you don’t need a separate line, and the Apple Watch will use your iPhones cell service/WiFi connection when in Bluetooth range of your iPhone.

Hope this helped, if you need more information, don’t hesitate to reply and ask for assistance. Have a great day.