The contacts stored on the OnePlus smartphone can be edited at any time if any information has been entered incorrectly or another detail has been added.

When editing, it makes no difference whether information is added or an existing detail field is edited or even deleted.

Android 10 | OxygenOS 10.0
Step 1:  Open the  Contacts app
Step 2:  Choose a  contact
Step 3:  Tap on  Edit
Step 4:  Select a  field
Step 5:  Enter the appropriate  data  
Step 6:  Tap on  Save
  1. Open the Contacts app
  2. Choose a contact
  3. Tap on Edit
  4. Select a field
  5. Enter the appropriate data 
  6. Tap on Save

OnePlus Instructions