I apologize if this has come up before. I didn't see it here and was surprised it worked. This is especially helpful for Verizon customers and exploits a couple of things. One is the manual entering of phone numbers when creating a POI and the other is our favorite trick, the NAV override. A well known workaround for entering phone numbers is to create a POI and put the phone number there. If you need to make a call, just scroll the map to that icon and tap it. You get the name and an INFO button. Press that and there's an icon for dialing. The problem is that it's ghosted when the car is moving. Here's where the NAV override trick comes into play. Just do that and the INFO button is now active. This way you can make a call. Yeah it isn't as good as the real phonebook (which won't work when moving) but it's at least something. I use the one-touch for frequent calls the the POI method for ones I do just once and a while.
Nice tip, pretty cumbersome, but still a useful work-around if you've filled up all your 1-Touch spots.