If we receive a call at an inconvenient moment, we can simply reject or dismiss it by swiping the red decline icon on the Xiaomi smartphone screen.

Android 11 | MIUI 12.0
Step 1: Drag the  Phone button  downwards
Step 2: Release the  Phone button  to reject the call
  1. Drag the Phone button downwards
  2. Release the Phone button to reject the call

Xiaomi Instructions