Openline pairs cleanly with a T-Mobile US primary line. Your T-Mobile US SIM (physical or eSIM) keeps handling your personal calls, SMS, and 2FA; Openline handles cellular data at travel prices.

How to set it up

  1. Install Openline as a second eSIM. Do not remove your T-Mobile US line.
  2. Once both lines are visible, set Cellular Data to Openline for the country you're travelling in.
  3. Keep Default Voice Line on your T-Mobile US line so calls to your regular number still reach you.
  4. Turn Data Roaming off on the T-Mobile US line so it never accidentally picks up expensive roaming.
  5. Turn Data Roaming on on the Openline line — that's required for travel eSIMs by design (Openline isn't charged as roaming to you).

Notes for T-Mobile US customers

  • Wi-Fi calling on your T-Mobile US line keeps working while Openline runs — a helpful failsafe when a hotel Wi-Fi is decent but a partner cell isn't.
  • If you have T-Mobile US's built-in international roaming plan, disable it before your trip or you'll double-pay: Openline will handle data, and your T-Mobile US plan will still bill you for it if left on.
  • T-Mobile US may occasionally push a "Welcome abroad" SMS. Ignore it — it's informational, not a bill unless you actually use their roaming.

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.