Global travel pass not working

I have a Premium Unlimited plan and am currently traveling in South Korea. When I landed in Korea, i received a welcome message for GTP and thought it was activated. But data is not working while call and texts are working.

I tried:

- Enabled data roaming(before departure)

- air plane mode turn off/on

- device restart

- device network reset

- network manual selection

but still not working.

can i get further help?