Preferred Roaming List...VZW changes it now and then, theoretically to prioritize the order of the list of 'Preferred' towers to use when you leave your home area and supposedly to let you use the cheaper roaming tower.
I know mine has always begun with 150xx and don't know anything about the 5xxxx numbers.
Just freaked out a little, ended the call, then I let it go through when it tried it the second time after seeing this thread, no idea what my PRL was prior to this, but it is now 52686 (philly suburb)
According to Verizon a 4G phone should never call #22899. My first phone did it and my signal strength got really bad. I called and they sent a new phone but after about a month it started up again. This time they told me to change the sim card (they said calling 22899 damages the sim card and will affect the signal strenght) but it started up again. This time they said it had something to do with their cell towers in my area. Still waiting for a call on the ticket they opened. I'll keep you posted.