[Freeswitch-users] change P-Asserted-Identity

HI, We have a dial plan that we require our customers to send us the Dial Number with a custom prefix, let's say 7000. We use this prefix to know where to route the call. We will strip the prefix and dial the correct number (sofia/internal/1xxxxxxxxxx;npdi=yes@xxx.xxx.xxx.xxxx:5060) On the 183 the pcap shows P-Asserted-Identity: "7000xxxxxxxxxx" <sip:+7000xxxxxxxxxx@xxx.xxx.xxx.xxx> I have no idea how that prefix got onto the P-Assereted-Identity. Can someone help me know how to change that to the real dialed number and strip the prefix?