Step 1, Launch iTunesStep 2, go to the menu “edit”--> "preferences” 
Step 3:go to "devices” and select "disable auto sync for iPhone and iPod” and then go to "ok"
How to turn off auto sync on iTunes?
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Step 1, Launch iTunesStep 2, go to the menu “edit”--> "preferences” Step 3:go to "devices” and select "disable auto sync for iPhone and iPod” and then go to "ok"