Huge issue with my phone! Need tips on how ot fix it!

I'm not sure where to start!! Non of the buttons work, Phone, End, Volume control, Menu list (at top left), Camera, Keyboard, Back. But I can still turn the phone on by holding the End button, I can't turn it off without taking the battery out however. The screen stays on, the phone calls the last person I called, it will open and close the calender randomly. If i'm sending a message (only by touchscreen because the keyboard doesn't work) it will exit the message and bring up the calender and I have to start all over with what I was texting. Once I get in to something on my phone, I can't get back out of it without taking the battery out. My warranty is most likely up and this is a 3 month old phone. AT&T sent me a newer one cause my other one was completely broken just after a year. I can't be without a phone because of my business. The touchscreen works fine which is the weird thing. When the calender randomly comes up, I can't use my phone at all because I can't close the calender because the Back or End button don't work. The phone did not get wet and this started about 2 days ago.

Right now the phone is on, i've been staring at the calender for the past 5 minutes waiting for it to go away. I have the screen set to 8 seconds before the backlight turns off, it's been on for 10 minutes now.

Would it be worth going down to AT&T and asking for another phone? It's only 3 months old and I don't see how thats fair if AT&T sent me this one when my other one broke and this one is already broken. My 2 year plan ends in December.

Also, for some reason the phone can't send or receive pictures even though it's in my plan. Not sure if thats the phone itself or just AT&T.

How do I do a factory reset on these phones?

It didn't change anything. Buttons still do not work. I'll stop by an AT&T later today.

The calender hasn't come up since I turned it off yesterday. When i turn it on it still calls the last person I called however.