let's try this one from scratch
--------------------------------

<<<< sip.conf >>>>
[vg]
disallow=all
allow=alaw
allow=ulaw
type=friend
;the ipaddr of the vg
host=10.0.5.5
insecure=yes
canreinvite=yes
context=from-vg
dtmfmode=rfc2833

[7903]
disallow=all
allow=alaw
allow=ulaw
type=friend
; the ipaddr of the phone
host=dynamic
context=from-vg
canreinvite=yes



<<<< extensions.conf >>>>
[from-vg]
exten => 5454,1,Dial(SIP/vg/5454)
exten => 5454,2,Hangup()

exten => 7903,1,Dial(SIP/7903)
exten => 7903,2,Hangup()


<<<< cisco vg >>>>
voice-port 2/1
  station-id 5454

dial-peer voice 5454 pots
  port 2/1

dial-peer voice 7903 voip
  destination-pattern 7903
  session protocol sipv2
! the ip addr of the * box
  session target ipv4:10.0.5.11:5060
 codec g711ulaw
!
sip-ua
! the important stuff is
! the ip addr of the * box
  sip-server ipv4:10.0.5.11:5060
!
end