You turned off code completion correctly. But parameter hints are still active. Turn them off by going into the Settings menu, searching for editor.parameterHints.enabled, and un-checking the box.
Or put the following entry in your settings.json:
"editor.parameterHints.enabled": false
If you ever want to see the parameter hints on-demand, refer to How to trigger parameter hints in Visual Studio Code?. In short, for Windows/Linux, Ctrl+Shift+Space; for Mac, Cmd+Shift+Space.