When you go the Cloud app on the phone, tap the three horizontal bars on the top left of the screen. Then tap Settings, at the bottom, and there should be options, What to Back up, How to back up, When to back up, etc.
Under what to back up, you can check or uncheck stuff - I only have contacts checked, nothing else, as my photos and other stuff is backed up to google, as are my contacts. But I like to use Verizon messages, and that only seems to pick up contacts backed up to the Verizon cloud, so I do use it for that.
