The following is an example for use in the asterisk extensions.conf file that
should allow you to terminate calls (dial out).
exten => _1XXXXXXXXXX,1,DIAL(IAX2/username@teliax/$\{EXTEN},20)

And the following line is an ex! ample of what is needed for TelIAX originated calls (incoming calls).
This example assumes you are using a SIP phone but a SIP phone is, of course, not required.

exten => 5033595555,1,DIAL(SIP/user,20)