Private Number Service on Asterisk + libss7/chan_ss7

Hey Everyone,
I’ve got an Asterisk Box with chan_ss7 connected to SS7 network using Digium card.
Everything is working great, however I need to setup a “Private/Hidden Number” service for some of my extentions.
Unfortunately I cannot just cut or change the numbers in dialplan, as SS7 operator wont accept any “fake” numbers.
I experimented with the SS7 Calling Nature of Address indicator, but it turned out it is hardcoded into chan_ss7 and it only supports National/International type and not Unknown. (correct me if I’m wrong here please and is private number service even related to SS7 NAI ?)

What I am interested in is “what is the proper way” of configuring Private Number scheme for Asterisk+SS7.
Which parameter is responsible for it ?
In addition in case this service can be configured easily on libss7, I would be happy to switch.

Any kind of input would be appreciated.
Thank you in advance.