Samsung Galaxy Note II (Sprint, US Cellular)

More frequently lately my Note 2 sounds very tinny and loud when making and receiving calls.I joke with a friend that it sounds like she is standing right behind me. Before, I would hang up and redial to fix it it. Now that doesn't work any more. I thought it was a reception issue. Any ideas what might be happening? Has it happened to you?
I'm due an upgrade next month but I would like to keep this phone longer if possible.

-Thanks