If you have a customer with an Asterisk server, the following Asterisk configuration will allow the Asterisk to send calls to your trunk group.

type=peer
trustrpid=yes
session-timers=refuse
rfc2833compensate=yes
qualify=no
nat=no
insecure=port,invite
dtmfmode=rfc2833
fromdomain=somedomain.15611.service
host=[resellerid].hpbx.outboundproxy.com
disallow=all
context=from-pstn
canreinvite=no
allow=ulaw&g729 

The corresponding SIP trunk configuration inside SkySwitch would appear as follows:

Note that the Asterisk will need to call a telephone number with a "1' prefix, or a valid extension (User, Auto-Attendant, Conference Bridge or Call Queue) within the domain to which it is assigned.