How do I turn off active hours on a VPS?

The best way to stop your server from automatically installing updates is to use the command linen SCONFIG option: -

https://blogs.technet.microsoft.com/mu/2016/10/25/__trashed/

Here is a more detailed explanation of why and how you can do this: -

https://micoolpaul.wordpress.com/2017/05/08/taking-control-of-windows-server-2016-updates/