OnePlus
Enable or Disable Contact Suggestions auf OnePlus
Gboard on OnePlus phones does more than suggest words and emoji. It can also scan the text field you are typing in and offer a matching contact from your phone book, for example when a form asks for a name or email address.
This behavior comes from a dedicated text correction setting inside the keyboard app, not from the OnePlus system settings themselves. It only affects Gboard, so switching keyboards would also remove the suggestions, but that is a bigger change than most people need.
Where to find the toggle
Open Settings ➔ System ➔ Languages & input ➔ Virtual keyboard ➔ Gboard ➔ Text correction. Inside that screen, find Suggest Contacts and enable or disable it with the switch.
Turning it off stops contact names, numbers, and email addresses from appearing as suggestions above the keyboard while you type. Turning it back on restores the quick-fill behavior for forms and messages.
If suggestions still appear after disabling this option, check whether autofill from your browser or a password manager is inserting the same data through a different path. That runs independently of Gboard and needs to be adjusted separately.