Check out this presentation from Kevin Mitnick. Basically, run a toll-free number to your asterisk box (with SIP), since your paying for the call, You have a right to know the billing number, even if the CPN is blocked (at least this is true with some providers). I did this back in 2009 or so, I think I was using flowroute. EDIT: To be honest, now that I got to re-watch the video (no sound..wtf), I might have given you mixed up information. They're (flowroute) allowing you to see the p-asserted-identity with a toll-free number. It still unblocks the caller ID, and I have read in various other places that owners of toll-free numbers are entitled to see your ANI, but I might be wrong in saying p-asserted-identity is equivalent to ANI (? I think its just plain caller id) Although my memory on all this stuff is hazy,I feel like I was able to filter out payphone origination to my toll-free when I was messing around with it, because I remember wanting to avoid the surcharges. How else could I have done that without ANI? Unfortunately I really don't remember since it was a good while ago. The more I read, the more Im convinced I remember correctly. Pretty sure flowroute passes you everything with a toll-free. EDIT: I can say I'm certain you get the Calling Party Category or ANI2 digit, and unblock caller ID with a toll-free number, but I never really tried to get the billing number/ANI itself in SIP, so I can't say for sure whether it's possible. I'm trying to find out more information on that specifically. Check this out apparently flowroute definitely does what you want it to, and I'll bet plenty of other SIP providers do as well (Wonder if its possible for any providers to do this without toll-free?): https://blog.flowroute.com/2015/08/27/using-advanced-signaling-to-detect-call-center-fraud/Apparently you can unmask alot of caller information including ANI over SIP, including the ANI2/CPC digit, amongst other things, so this thread is still a valid answer to your question.. Just wanted to verify I wasn't recalling anything incorectly.