An eSIM does not replace your SIM. It is an extra line in the same phone, as if you had two numbers.
What stays the same
- Your number. The physical SIM stays in the phone and keeps receiving calls and texts, bank codes included.
- WhatsApp, Viber, Telegram, Signal. They are tied to the number, not the card. Same number, just over eSIM data.
- Your apps and accounts. Nothing resets and nothing needs signing in again.
What you change
Exactly one thing: which line carries mobile data. You point that at the eSIM and leave calls and texts on your own number.
How to avoid accidental roaming
Turn data roaming off for your home SIM. Then not a single byte can go through your own operator, even if an app tries.
On iPhone there is one more trap: Allow Cellular Data Switching. With it on, the phone falls back to your own SIM when the eSIM signal dips. Turn it off.
Calling home
Apps are cheapest, because they run over data. A normal call from your own number while roaming is billed by your operator at their rates.