SIP INVITE header

[utwo]

Hi, all,
Is it correct that FROM and TO ip addresses are same? Is it possible to change ip address of FROM header?

Outgoing call from IP Office to ISP side:
A.A.A.A - ip address of IP Office 500 side
B.B.B.B - ip address of ISP side
7777777777 - calling number
999999999 - called number

17:26:18    3208650mS SIP Tx: UDP A.A.A.A:5060 -> B.B.B.B:5060
                    INVITE sip:999999999@B.B.B.B SIP/2.0
                    Via: SIP/2.0/UDP A.A.A.A:5060;rport;branch=z9hG4bKaf2c3e6ce1ecceda0a5f97e38828d8e7
                    From: "7777777777" <sip:7777777777@[b]B.B.B.B[/b]>;tag=18f95daa0a1f2cab
                    To: <sip:999999999@[b]B.B.B.B[/b]>

http:\\itscom.kz