iPhone 5 not sending texts PLEASE HELP!!!

Hey, I have had this problem for over 3 weeks now. I've searched all the forums and came up with nothing helpful. Tried every possible solution, nothing worked. My problem is this: My iPhone 5 won't send SMS text messages. I try to send, and the "sending" bar gets to about 95% then says "message not delivered". I am running iOS 6.1 (10B143). I just recently got Verizon's share everything plan so I could text, and I must say, it's very aggravating that I'm not able to. Please help! I'm very frustrated right now and all my searches (I've been very thorough) have come up with nothing.

Thanks,