I have a LG Fusic which is just a few version above your LG 500.
I was trying to do exactly what your question ask for and did A LOT of research for it.
The problem (at least for Fusic) is the capability of the bluetooth (or the stack) on the phone.
Between the phone and pda, you need a "serial port" connection, but all I get is "Dial-Up Networking" Connection.
"Dial-Up Networking" connection is for phone act as modem... and nothing else.
So, my phone can transfer contact, transfer files, and dial as modem (if I paid for the service), but without the "serial port" capability, it will not dial from your PDA. So "Dial via bluetooth" will not work for LG 550 (aka Fusic).
You can check what the phone supports under tools-->bluetooth-->supported device. If your LG 500 has the "Serial Port" connection, Great. If not, then you can't dial via bluetooth from you pda.