iPhone is constantly syncing when connected to my PC. I turned off auto sync and it still synchs every couple of minutes

How do I stop my iphone from constantly synching/backing up with iTunes when plugged in. I tried removing the "auto sync on connection" setting, but it still syncs every few minutes.

There have been no environment changes and it was working fine until a couple of days ago. I've re-booted my PC, my iPhone and iTunes but it hasn't helped