Total disabling of the wifi on KA1

Hi, I would like to disable compleately the wifi connection on my kobo.
Is there a way to do it modifing an internal system file? (for example renaming a file or using notepad++ on a file)

(I think that in some way the wifi connection remains enabled and I don't like at all to be spied by kobo or by others...)

I appreciate any idea or participation