To do it through iTunes, you have to be sure you didnt update it there or sync your iPhone with the new version of FB.
If you havent done either, delete it from your iPhone (press & hold the FB icon) and then sync it with iTunes. Once its done, under your iPhone, go to the Apps tab, and Facebook should be unchecked, re-check it.
Since you didnt update it on iTunes, it still has the old version.
Thank you so much, this worked.