My iphone 4 has been dropping 90% of my calls, screen not responsive, nonstop

[inscrutable]

vibrating? I bought my iPhone 4 in August 2011 so I haven't even had it for a whole year. About a month ago, it started dropping calls. I wouldn't be able to hear the person on the other line, but they could hear me. Then, the phone would just end the call (not even call failed). As time has passed, that problem still exists except now its with almost every call that I can't hear the person on the other line, or after I pick up the call I can't hear anything and then it just "call failed" me. It might do this 10 times in one conversation. Also, what happens sometimes is that when I'm on a call and want to navigate away from the call screen, the screen does not respond. I can't touch speaker, mute, etc. even if i press the home button I can't touch anything on that screen either. The next problem I had occurred this morning. After receiving a call (and having it be dropped) it would not stop vibrating for over 40 minutes until I pressed home and lock for 30 seconds.

I don't know if I should take it to the ATT store or the Apple store. I kind of just want a new iphone 4.
This is becoming to be so effing annoying. I have a boyfriend in the military and need to be able to answer my phone and have a reliable conversation at any given time that he can call. It's also a pain in the ass to call companies because after being on hold for what feels like days, I don't appreciate my call being dropped and having to start over.

What should I do? Anyone else have this problem?