Freepbx one-way audio trouble

Hi, I have FreePbx installed from iso on a bluehost server. I can register my sip phone, I can make inbound and outbound calls. The only problem is there is one-way audio on the call. If I call from my Windows Sip phone to my cell phone -- My cell can hear me, but I cannot hear the cell. If the cell phone calls my Windows Sip phone -- The cell can hear me, but I cannot hear the cell. I suspect it's something to do with Ports 10000-20000 but have no idea where the set those up on FreePbx.