When inserting a Korea SIM card or setting up eSIM Korea into your phone, it’s possible that LTE data works fine, but calls and texts do not come through.
Why does this happen?

To use voice and text services on the KT mobile network in Korea, your phone must be compatible with WCDMA ~ HSPA (3G) / HSPA+ (4G) networks.

How to Check Your Phone’s Network Mode

1. Open your phone’s Settings app.
2. Go to Connections (or Mobile Network, depending on your device).
3. Tap on Mobile Networks.
4. Select Network Mode.
5. Make sure the setting is LTE / 3G (WCDMA) Auto-connect.

If your phone is set to LTE/CDMA, it may only support data — and voice/text may not work in Korea.
Tip: Before arriving in Korea, please check and adjust your phone’s network mode settings to ensure full compatibility with eSIM Korea or Korea SIM services.

Please make sure that you check Network mode on your phone before you come to Korea.