After enabling the data warning on the OnePlus smartphone, we can set a limit that we will be notified when the data warning is exceeded.

Note: We recommend a data warning limit of approx. 80% of the actual data volume to be able to react in time before the limit is used up.

Android 10 | OxygenOS 10.0
Step 1:  Open the  Settings
Step 2:  Tap on  Wi-Fi & network
Step 3:  Tap on  Data usage
Step 4:  Tap on  Billing cycle
Step 5:  Tap on  Data warning
Step 6:  Set the  data warning  and tap  OK
  1. Open the Settings
  2. Tap on Wi-Fi & network
  3. Tap on Data usage
  4. Tap on Billing cycle
  5. Tap on Data warning
  6. Set the data warning and tap OK

OnePlus Instructions