I want to know if my phone will work on February 22
I assume you are on AT&T, otherwise that Feb 22 date means nothing.
The Galaxy S3 is NOT on AT&T's support list. So, no, it won't work.
In fact, I'm surprised AT&T hasn't already deactivated the SIM card on you, or that you haven't received a free supported device from them by now.
Unless you are on an MVNO carrier that uses AT&T's network. In that case, you may not get anything beforehand.
If you are not on AT&T at all, then relax. That date doesn't apply to you.
That doesn't mean that any other carrier doesn't have their own 3G shutdown dates coming. And they do.