sip.conf:

[general]
context=default
bindport=5060
bindaddr=0.0.0.0
srvlookup=yes
dtmfmode=rfc2833
relaxdtmf=no
disallow=all
allow=ulaw
allow=alaw
allow=gsm
maxexpirey=30
defaultexpirey=180
canreinvite=yes
nat=0
UserAgent=Asterisk

[didnumbers-us1]
host=us1.didnumbers.com
type=peer
insecure=port,invite
disallow=all
allow=alaw
allow=ulaw
allow=g729
allow=gsm
allow=g723
dtmfmode=rfc2833
[12104686218]

context = default
type=peer
defaultuser=******
insecure=invite
secret=*******
;nat=yes ; This phone may be natted
host=dynamic
canreinvite=no ; Cisco poops on reinvite sometimes
disallow=all
allow=ulaw
allow=alaw
allow=g729

extensions.conf:

[general]

[default]

exten  => 12104686218,1,Answer()
exten  => 12104686218,n,Playback(hello-world)
exten  => 12104686218,n,Hangup()





exten => _XXXXXXXXXX,1,NoOp(Dialing out)
exten => _XXXXXXXXXX,n,Dial(SIP/us1.didnumbers.com/${EXTEN})
exten => _XXXXXXXXXX,n,Hangup()