Trixbox has what i consider to be a strange behaviour where an extensions Outbound CID will override the trunk CID.
Using engin, i wanted to supress caller id on all outgoing calls. This is easy, i hear you say just by prefixing numbers with 1831. For engin, this works for everywhere but an 07 number. I called them about it and they told me that its not a problem at their end. This seemed strange to me as other Australian numbers worked perfectly. Anyway, i discovered that if you use a PAP2T or a SPA-3000, and supress caller id with them, the CID sent to engin is “anonymous”.
I now knew how to supress it but had trouble getting trixbox (or FreePBX) to actually use it. I decided that I could use the “Emergency CID” field in FreePBX Extensions and only mark engin as the emergency route. Then on the outgoing routes, tick Emergency for the numbers you want to supress caller id on.
I know its a bodgy solution but it works and i would present a normal CID for emergency calls anyway.