For example, if we are abroad with the OnePlus smartphone and want to avoid additional costs, a call barring function can be activated which blocks the corresponding outgoing or incoming calls.

The following options are available to us in the phone app

Note: When using Dual SIM, call barring can be set up individually for each SIM card.
The call barring password must be requested from the relevant network operator.

Android 10 | OxygenOS 10.0
Step 1:  Open the  Phone app
Step 2:  Open the  menu
Step 3:  Open the  Settings
Step 4:  Tap on  Call accounts
Step 5:  Choose a  SIM card   (Dual SIM)
Step 6:  Tap on  Call barring
Step 7:  Choose an  option
Step 8:  Enter the  password  an tap  Turn on/off
  1. Open the Phone app
  2. Open the menu
  3. Open the Settings
  4. Tap on Call accounts
  5. Choose a SIM card (Dual SIM)
  6. Tap on Call barring
  7. Choose an option
  8. Enter the password an tap Turn on/off

OnePlus Instructions