The WLAN hotspot uses the mobile data to share the Internet with other devices. If no Internet flat rate is available, it is recommended to activate data restriction. If the defined data limit is reached, the WLAN hotspot will be deactivated.

If the personal hotspot is reactivated after the limit is reached, the data restriction is reset.

Android 10 (ColorOS 7.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Other Wireless Connections
Step 3:  Tap on  Personal hotspot
Step 4:  Tap on  Connection management
Step 5:  Tap on  Data restriction
Step 6:  Choose desired  Limit
  1. Open the Settings
  2. Tap on Other Wireless Connections
  3. Tap on Personal hotspot
  4. Tap on Connection management
  5. Tap on Data restriction
  6. Choose desired Limit

Oppo Instructions