Bluetooth in 2004

Hello!

My Prius is a 2004 with the Nav system and bluetooth, I bought it used off a 'back yard dealer lot' as is so there is some wear and tear. One thing that I find extremely irritating is that I have bluetooth in my car but I can't use it because the person on the other end of the car can never hear me. I can make and receive calls just fine, I can always hear the person I'm talking to through the speakers of my car but 90% of the time the person I'm speaking with says they cannot hear me that I sound fuzzy.

I would prefer to try and fix this issue myself, I really don't want to go to a dealership and pay to have the problem fixed if this is something I can take care of for myself. Thanks in advance!!