http://en.wikipedia.org/wiki/Private_network
10.0.0.0 – 10.255.255.255
172.16.0.0 – 172.31.255.255
192.168.0.0 – 192.168.255.255

These are the private networks. The IP address on the phone is a private one, the NAT is performed on the other end i.e. provider side. You can`t do nothing to change NAT settings, except contact them but I reaaly doubt that this will help.