First, please be careful when accessing the debug menu. This is a warning to those of you that may not want to attempt doing things that are not "supposed" to be done by the customers.
You can access the debug menu by following these steps:
Power off the phone
Power on the phone
Wait for the power-on animation to complete
Press F (right on the 4-way navigation button)
Press 0
Press 0
Enter 000000 (6 zero's) for the "FSC Code"
press "OK" (middle button inside the 4-way navigation button)
Here are some descriptions of what can be changed, posted in message #789 by fmagidson:
I personally am not planning to move to sprint pcs, but some of the
rest of what Craig (cgafah@y...) posted the following on the
alt.cellular.verizon and alt.cellular.sprintpcs newsgroups 01-24-03
might be interesting:

Some of you may already know this, but the Verizon Audiovox CDM 9500
has some pretty nifty field debug menus as well as some additional
menu functions not in the 9155 field debug screen. In order to
enter this mode, you need to key function 0,0 as soon as you power
up the phone. Then enter 000000 as the FSC code. At that point you will be in the debug menu. Some of the functions allowed in
this debug menu are:

• Forcing Sprint PCS

If you are on an Americas Choice Plan, you can force Sprint PCS (and incur no roaming costs to my knowledge) by going to "Pref. mode" option, then "PCS channel" mode and keying in the primary active PCS channel (carrier frequency) in your market. Here in NJ, the primary carrier frequency for Sprint is 650. Key that in, and you have just effectively forced Sprint. There will be a little triangle next to the signal bar to indicate that you are on a different network, but the digital "D" will obviously still be there. It will stay on Sprint indefinitely(until you change it) and you will be able to make and receive calls without a problem. Setting the option to "PCS only" mode doesn't work for some reason, so you will have to use the "PCS channel" option. In order to find the primary PCS channel or carrier frequency in your market, you may have to hunt a little but its pretty easy once you know which PCS spectrum block Sprint owns the license to in the area (A,B,C etc).

• Displaying Carrier Frequency information

The 9500 contains a debug screen that actually lists the carrier frequencies that are active in the area! I wish the 9155 had this. It is pretty easy to find, it's just in the option "debug screen", then "normal", then scroll through the menus until you get to active channel list. And there they are, you can use this screen in Automatic, or while you have forced Sprint. According to the screen, there are Six Verizon CDMA carrier frequencies deployed in my part of NJ, they are 384,425,466,507,548,589. Notice the 41 unit increments between each Carrier Frequency. I believe this relates to the original 30khzspacing used in the AMPS days to separate the channels. 30khz * 41channels equals 1.230 MHz, the width of a CDMA channel is 1.25mhz, so there you go, only a 5 kHz guardband between each CDMA channel. In total that's 7.5 MHz worth of digital channels deployed (really 15 MHz, I’ll explain later). I'm not sure how much Verizon owns in terms of the amount of spectrum in this market but I think its either 12.5 MHz or 15.0 MHz one way. Total is 25 or 30 MHz. A side and B side carriers have a total of 50 MHz together, 824 - 849 MHz up to base, and 869 to 894 MHz down to phone. Anyone remember this? Either way they are using over half of their spectrum for CDMA which is not surprising. Probably will increase even more over time. I was surprised to see that Sprint is only using two carrier frequencies in the area, 625 and 650. I guess they either don't have the demand in this market, or are using it differently, maybe Verizon doesn’t even need all those carrier frequencies deployed at this time, but they are deployed.

See More: 9500 Debug Menu