You are somewhere past the halfway point of a trip - say, day six of ten in Chiang Mai - when the signal bar on your data plan does the thing it always does. It thins. You are mid-map, mid-message, or mid-argument about which songthaew to flag down, and the thought arrives with unhelpful clarity: I am about to run out.
This used to be a genuine crisis. You'd need a shop that sold your carrier's top-up cards, in a language you didn't read, during opening hours you didn't know. Then you'd need to redeem the thing, usually by dialling a code that looked like a phone number having a breakdown.
None of that applies here. A travel eSIM doesn't run out and go dark - it runs out and asks, politely, for more.
What "topping up" actually means
Your eSIM is a profile, not a physical object, so adding data or days to it isn't a new SIM, a new QR code, or a new install. It's the same profile, given more room. Open the Sonet account page, pick the amount you want, and the extra data attaches to the plan already running on your phone. No reinstall, no new settings screen, no paperclip you don't have.
The whole thing takes under a minute, which matters more than it sounds like it should. The moments you need to top up are rarely convenient ones - a train platform, a queue for a temple, the back of a tuk-tuk - and "under a minute" is the difference between fixing it now and fixing it three stops later.