Open trunk or extension for MyPBX to connect to

You can either define new trunk with the following information on the
User Context =
User Details
type=friend
secret=1234Goip
qualify=yes
host=dynamic
dtmfmode=rfc2833
context=from-internal
canreinvite=no

However this option, it will not able to pass thru the a2billing since the accountcode is not defined.

To enable this, you need to define the account in the user context.

The other method is to define a new extension but for this option, you unable to pass thru the CLI as it will always follow the CLI defined at the extension level.