Diversion Header

I know that this is an Asterisk issue.

I have a client that on their key system has line appearances for each analog line and has 3 different companies. They know how to answer the phone stating the appropriate companies name because they know if line 1 rings it is company A and that if line 2 rings it is company B.

I need to mimic these settings so, I would like to use an ext (or use a ring group) with a forward no answer setup and use the diversion header information to display that ext so that they will know what company to answer the phone as.

We have Polycom phones setup to use the diversion header if it is passed, what we cannot figure is how to make get the diversion header added to the SIP invite.

We have tried adding the line to several different macro sections of the extensions.conf but cannot make get it to send an invite with the diversion header.

exten => s-NOANSWER,1,SIPAddHeader(Diversion: tel:${ARG1};reason=user-busy;screen=no;privacy=off

Can someone please assist in getting this corrected please.