We all receive unsolicited calls from companies telling us that we've won something or whether we're still interested in a gambling subscription. These are exactly the numbers that we immediately block without a second thought. It's a good thing that the feature is not hard to find in the recent calls or call log on the Xiaomi smartphone.

Android 10 (MIUI 12.0)
Step 1:  Open the  Phone app
Step 2:  Open the  menu
Step 3:  Tap on  Block
Step 4:  Confirm with  OK
  1. Open the Phone app
  2. Open the menu
  3. Tap on Block
  4. Confirm with OK

Xiaomi Instructions