SIP Display Info

I have an a problem registering a trunk that is driving me nuts. No matter what I try in the “register =>” command I cannot set the SIP Display Info element in the To and From headers. Seems like the trunk configuration parameters like fromuser/authuser/etc. do not affect in any way the register process so it must be my syntax for the register statement (which I saw got changed in 1.6) Is there a way to do this?

I’m running version

Why do you want to set them? They are not intended for machine use!

I know they aren’t. I’m trying to mimic e customized Windows SIP client by my SIP provider as they do not offer a Linux one.