Disconnecting from the Internet wouldn't have helped in the least since the OS had already finished downloading and was installing Mavericks from the hard drive.
The method documented here (right click on update, select Hide Update) no longer works. I have app Store version 2.2.1 (584), macOS Sierra version 10.12.6 (16G29). Macos mac-appstore software-update.
You had OS X, 10.7 Lion on the drive, not iOS anything. OS X is the operating system for Mac computers such as the Mac Pro, iMac, Mac Mini and MacBook Pro. iOS is a completely separate OS and is only for mobile devices such as the iPhone and iPad.
Since Mavericks is now on the drive, the only way to go back to Lion, which your Mac came with, is to do an Internet Recovery. You WILL lose everything on the drive. Make sure to back up files you cannot afford to lose, first.
Stop Software Update On Mac
Latest Mac Software Update
Restart and hold down the Command+Option+R keys. Launch Disk Utility and erase the drive. Then install OS X. The version of Lion that came with your Mac will download from Apple's servers and install.