Phone listed in Device Manager isn't mine I have found two phones in my Device Manager that I don't recognise, in fact if I'm not mistaken they appear to be phones that are on American networks but I live in South Africa. They were last online a few months ago (May 2016) but nonetheless I'm concerned about the security of my account. I would also like to remove those devices from my manager. What should I do?
Follow the instructions below. I suggest you should change your password just in case. 


Use your phone's browser to go to myaccount.google.com. 
In the "Sign-in &amp; security" section, touch Device activity &amp; notification.
In the "Recently used devices" section, touch Review devices. 
Touch the device you want to remove > Remove.


Source: https://support.google.com/accounts/answer/6264236?hl=en