messages app keep crashing

heeeeelp! my iphone 4 is not letting me use the massages app properly. :/

the messages app repeatidly crashes. it happens in a pattern. when i first do one of the many ways to solve the problem, it wom't let me open the app at all, just crashes right after. second time i try to fix it, it will let me have a conversation with ONE person, but will not let me go back to the conversation list to view any other messages. & lastly, it will finally let have conversations with multiple contacts as well as let me view the conversation list, but once i try to scroll down the list, it'll freeze & crash right back to the home screen.

i've done EVERYTHING to fix it, from turning the phone off & back on, hard reset, reset all settings, restore iphone on itunes, & took it to apple to get it replaced TWICE! & the problem is still happening. nobody in apple stores know what this problem is.