Oppo
Turn Automatic MMS Download On or Off auf Oppo
Oppo phones running Coloros download MMS attachments in the background as soon as a message arrives. This happens over mobile data by default, which is why unexpected data usage on a metered plan is often traced back to this setting.
On dual-SIM devices the option applies separately to each SIM card, so disabling it on one line does not affect the other. That is a common source of confusion when only one number keeps downloading MMS automatically.
To change it, open Tap on Messages ➔ Open the Menu ➔ Tap on Settings ➔ Choose a SIM card (Dual SIM) ➔ Enable or disable Auto-download MMS.
Turning the option off does not block MMS messages entirely. You still see that a message arrived, but the attachment only downloads once you open it manually, typically over Wi-Fi if available.
Leave it enabled if you regularly rely on MMS for photos or group texts and are not concerned about data usage. Disable it when you want to control when larger attachments are pulled, especially while roaming or on a limited plan.