When I last tried to do it on a friends desktop I found out that they made it harder. IIRC they decided to deprecate gui app that could do it. 
And I couldn't open that app... Is it the method/app you used?
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I only use services.msc ( the normal service app in windows ). Type services in search, scroll down till you see windows update and just disable it's service.
typically it works but it could be that newer updates have task scheduler checking if updates service is on or not. For that you might need group policy editor.
since I'm using windows 10 home they disabled the gpedit or Group Policy editor however you can easily bypass that.