If the Huawei device is connecting to a foreign or unknown network, there will be no data packet sent unless roaming is turned on. Only if roaming is activated, you can use the mobile data network of a foreign country, this can (and mostly will) lead to additional costs.

Note: In european countries you can use EU-Roaming and use your internet as if you were at home. We still recommend to talk to your carrier first.

Android 10 | EMUI 10.0
Roaming -  Open the  settings
Roaming -  Tap on  Mobile network
Roaming -  Tap on  Mobile data
Roaming -  Activate or deactivate  Data roaming
Roaming -  Confirm with  OK
  1. Open the settings
  2. Tap on Mobile network
  3. Tap on Mobile data
  4. Activate or deactivate Data roaming
  5. Confirm with OK

Huawei Instructions