To stop this service, open [Command Prompt] (Start>Run>cmd>Enter) and type the following command sc stop wuauserv. This will not prevent Automatic Updates from starting at the next boot. So don’t worry, you’ll keep getting Windows updates. Just don’t forget to restart eventually.

Now, to get rid of it:
Start / Run / gpedit.msc / Local Computer Policy / Computer Configuration / Administrative Templates / Windows Components / Windows Update / Re-prompt for restart with scheduled installations