Oppo
Turn Mobile Data On or Off auf Oppo
On an Oppo phone, mobile data is the single switch that decides whether your device uses the cellular network for internet access once you leave a Wi-Fi network. ColorOS keeps this setting separate from flight mode and from individual app permissions, so a working SIM and a valid tariff plan are not enough on their own.
To check or change the setting, go to Tap on Settings ➔ Tap on SIM card & mobile data ➔ Enable or disable Mobile data. On dual-SIM devices, confirm that the SIM assigned to mobile data is the one with an active data plan.
A valid access point (APN) must be configured for the mobile network to actually deliver data, even after the toggle is switched on. If mobile data stays on but nothing loads, the APN entry for your carrier is the more likely cause than the toggle itself.
Turning mobile data off is useful when you want to force all traffic through Wi-Fi, avoid unexpected charges while traveling, or troubleshoot whether an app problem comes from the network or from the app itself.