Support Phone shuts down randomly without warning

view story

http://androidforums.com – My galaxy attain 4g started off doing a reboot on its own a few times a day. Now, it just shuts down completely without warning, doesn't matter how full my battery life is. I did a system restore, an update, a new battery, everything... and nothing works. I sent it in to Samsung, they told me they "replaced the component" and the very next day AFTER I got it back, it did the exact same thing. I'm stuck with this phone and I don't know what to do anymore, it dies on my randomly. I'm still under warranty but they don't even fix it when I send it in! Suggestions? Does anyone else (General)