Disable Windows Update in Windows 10 IoT Enterprise

I'm trying to disable the Windows Update service to stop it from running and downloading updates while our device is connected to the Internet. Our device is only connected on occasion and remains offline most of the time. I have tried multiple registry settings for the update service and related services, but as soon as it sees a connection they start back up.

I found some group policy settings to stop update from automatically downloading and installing them. Is that the only way to keep updates from happening?

Thanks,

Josh