The process is simple, and if you want it to be, My Magazine could be out of your hair within minutes if not seconds. First thing you need to do to cancel this magazine subscription is to launch the settings application on your Galaxy S5. Scroll all the way down and under the Applications setting, tap on Application Manager. Swipe to the All section, scroll down to the "M's" and click on My Magazine. Click on Turn Off, and then confirm your actions by tapping on Ok.
All you need to do to bring back My Magazine is repeat the process and you'll be given the option to turn on the feature. Now that wasn't too hard, was it?