With two lines on one phone, you pick which one does the data. When you land, that's kimsim.
iPhone
- Settings → Mobile Service → Mobile Data.
- Choose the kimsim line.
- Leave Allow Mobile Data Switching off, so the phone doesn't quietly fall back to your home line and its roaming charges.
Pixel and most Android
Settings → Network & internet → SIMs → choose kimsim → turn on Mobile data. Then turn mobile data off on your home SIM.
Samsung
Settings → Connections → SIM manager → Mobile data → choose kimsim.
Don't forget
Turn on Data Roaming inside the kimsim line too.
Can't find the Mobile Data option at all on iPhone? It hides when no line is connected yet. That's this one.