windows 10 - Cannot delete scheduled task

There is an issue on a system that the windows updates can not be disabled. (I tried with group policy, settings, registry and services)

Once I disable the "Windows Update" from services.msc, somehow it changes from "disabled" to "demand start".

I think the problem is Task Scheduler.

When the "Scheduled Start" task runs, I found the "Windows Update" service option changed from "disabled" to "demand start". (the task trigger is "One time" but after it changes the option as "demand start", the trigger date was incremented by 1. So, everyday at the same time, the system changes from "disabled" to "demand start" if the option is "disabled")

So, I tried to delete the "Scheduled Start" task, but I failed. (tried to delete from folder C:\Windows\System32\Tasks\Microsoft\Windows\WindowsUpdate, and that was also not effective)

Editing was also blocked.

Is there anyway to delete or change the "Scheduled Start"?

Scheduled Start image