What do I do if all my calendar and contact information is gone.

My business depends on syncing my data. Of late, I can have all my canender events and contacts dissapprear from my iPhone. I have been to the Apple Store twice. It gets fixed for a day or two, then everything is gone. I have deleted my account then bringit back, turn off and on syncing and thrown it out the window (no, not really, but the impluse is there). Anyone know of something more realiable at keeping data on the iPhone?