Sprint contacts syncing between 2 phones?

I have a new sprint 2 year contract that has 2 phones on it (both being LG optimus s) and for some reason the contacts always sync between the 2 phones. No matter how many times I delete them from one phone they just sync right back. So what's the point of having 2 separate phones if all of the contacts will always be the same? Is there a way to stop them from cancelling? I unchecked the background data sending in hopes that it will work but I also want to know when I get new emails too so I need that checked.