Oppo
Turn Data Roaming On or Off auf Oppo
Mobile networks separate your home carrier from every other network you connect to. Once your Oppo phone leaves the coverage area of your own provider, it needs a separate permission called data roaming to keep using mobile data on a foreign network.
Without this permission active, calls may still work in some regions, but mobile internet stops the moment you cross the border. This is a deliberate safeguard, since roaming data is frequently billed at a higher rate than data used at home, especially outside the EU.
On ColorOS you manage this setting per SIM card. Open Settings ➔ SIM Card & Mobile Data ➔ select the SIM card you are using abroad ➔ enable or disable Data Roaming.
If you use two SIM cards, check the toggle for each one separately. A common mistake is enabling roaming on the wrong SIM slot while the travel SIM stays switched off.
If mobile data still fails after enabling roaming, the issue is often a missing or outdated APN profile rather than the roaming toggle itself. In that case, check your carrier settings before repeating this process.