Yup, the app is just a storefront to buy esims, it doesn’t have much innate to do with the function. Once you purchase one, it generates a link in app to install the eSIM, which your phone does its thing for 60 seconds or so. Then within your settings you presumably have something like a cellular tab as on iPhone. You simply turn off your regular plan and turn on the e sim line. When you are back home you just need to turn back on your regular line and off the eSIM (or delete it if you are done with it).
I actually now prefer on iPhone to go into my home plan and leave the cell phone plan on, but turn off data roaming within that line and keep the eSIM on with data as well. It allows you to have two plans connected to cell towers (at least mine does). What this does is prevents the iMessage connectivity from getting screwy. I can still receive texts for free or phone calls can ring (and I don’t answer them) and then I can freely iMessage people back for free and if they are a text contact I’ll WhatsApp.
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