iPhone has "Allow Cellular Data Switching" which auto-fails-over to your other line during weak signal. Turn it OFF: Settings → Cellular → Cellular Data → toggle "Allow Cellular Data Switching" off. This prevents surprise roaming charges on your home line.

Still stuck?

Reach Openline support 24/7 through any of these channels:

When you write in, include your purchase code (the OL-… code we emailed you) and, if the eSIM is already installed, its ICCID (Settings → Cellular → tap the Openline line). That's enough for us to find your plan and diagnose without back-and-forth.