[Serusers] How to remove npdi & rn parameters from INVITE messages?

[Frank Durda IV]

I have another large carrier that I am trying to send
calls to, and they have a requirement that you not send
them the npdi and rn=nnnnnnnn parameters for all calls.
If you do, the call handling will be botched and the call
will fail, even if the LRN information is exactly correct.

Apparently this carrier (who once owned the Death Star) is
incapable of filtering or ignoring this information on
their side, and the sending switch is incapable of not
sending this information because they thought RFC 4694
said they MUST ALWAYS send npdi/rn on every SIP call.
Of course, the RFC does not say this.  Don't get me
started on which party is dumber.

Anyway, I was hoping that SER could act as diplomat or
interpreter and with some rewrite-something() calls,
SER could remove the npdi/rn, or alter them to the
point that the receiving switch no longer recognized
the parameters as rn/npdi and so happily does it's own
thing, and the calls don't die.

However, based on what documentation exists, none of the
various rewrite functions appear to operate on this part of
the INVITE message and replace doesn't appear to work on the
first line of a message.   So there seems to be a spot
whose contents can't be reached or manipulated by the
existing functions.  Am I correct in thinking this?

So, is there a way to do something with rn=NNNNNNNNNN
and npdi/npdi=yes parameters without having to write
a custom function to do it?

Thanks in advance!