If they have access to your iCloud/Apple/iTunes account, then they can track your iPhone without you knowing it. You won't get any notification when they track your iPhone. That is how it works...Also they will be able to track your iPhone if you given permission to them to track your iPhone through the 'Find My iPhone' app on Computer or iDevices (like iPhone, iPad or iPod)If you don't want to be tracked, then you can turn off the 'Location Services' or 'Find My iPhone' from your iPhone. If you want to be it back on tracking, then you can turn them back on. Let me know if you have any further questions.