As time goes on and we approach July 29, 2016, it appears that Windows is getting more aggressive to get people to upgrade to 10. It is free up until that date on the device you have it on. On some systems, they have even started the download process to make it easier and faster for when you do upgrade.
If you have automatic upgrades enabled, you might find your machine already updated – and you didn’t even initiate it. If you aren’t ready for the upgrade, make sure to disable automatic updates and do them manually. Even doing them manually you will have to look at your list of updates and uncheck the Windows 10 upgrade to get the regular security updates for your version.
Here is some more information: