Yes, your SIP trunk provider can give you the list of DID's that are assigned to your main number. That info (or at least the ones that are assigned) should be accessible in the phone system you have as well in the administration portal. A DID (Direct Inward Dial) is really a way to dial someone directly rather than having to dial the main number and enter their extension. It is not tied to the number of lines (trunks) you have. Typically you will purchase a block of numbers from the carrier and assign them to users in the phone system (e.g.555-1234 maps to extension 102). So technically you could have 23 lines (trunks, channels, call paths) and 100 DID's.
I’m currently inheriting a phone system but I have more knowledge on the internal workings of a phone system than the external workings. I’m not opposed to seeking training but I’m not sure what path to go down for that or how to find that information out. As I resolve that issue I have two immediate issues I’m trying to resolve.
I’m trying to find out how many DID numbers we have and the phone/voice aspect of the network is poorly documented with respects to the phones. I have some of the DID numbers but absolutely not all of them. First I’m trying to comprehend a DID number’s purpose. Is it akin to a public IP address that is external facing, and if I chose I could have one DID number to an operator, and the incoming call could be routed to any number of internal numbers? If that’s the case I assume there would be some issues with having all voice traffic on the one number and that’s where multiple DID numbers come into play.
Aside from attempting to wrangle in the idea, is there a way to see how many DID’s my organization has ownership of? Is there a registry like with web domains or someway to find this information out?
Forgive my ignorance but I'm just dipping my toes into this aspect of the IT world.