We are using trixbox CE 2.8.0.3 with FreePhoneLine

Trunk Configuration:
PEER Details
type=friend
context=from-pstn
username=YourFreePhoneNumber
secret=YOU_HAVE_TO_BUY_THE_SIP_CONFIGURATION_FILE
fromuser=YourFreePhoneNumber
host=voip.freephoneline.ca
qualify=yes
insecure=very
nat=yes
canreinvite=no
fromdomain=voip.freephoneline.ca
sendrpid=yes
disallow=all
allow=ulaw&g729
Incoming Settings:
type=friend
context=from-trunk
username=YourFreePhoneNumber
secret=YOU_HAVE_TO_BUY_THE_SIP_CONFIGURATION_FILE
fromuser=YourFreePhoneNumber
host=voip.freephoneline.ca
qualify=yes
insecure=very
nat=yes
canreinvite=no
Register String:
YourFreePhoneNumber:secret@voip.freephoneline.ca/YourFreePhoneNumber