VoIP DiD server

Hello, We require the building of a VoIP Switch which focuses on inbound DIDs. It must handle 1000 concurrent calls. We have our own number range consisting of over 1000 000 DiDs It will have multiple trunks for over 10 providers who will send calls to this switch. The switch must accept the call and RECORD the IP/TRUNK/CHANNEL where the call is originating from. It must also route the call to the relevant SIP Account the DID is allocated to. We need to allocate a cost on each channel so each call has a cost to it based on prefix. At month end, we must be able to draw out a report stating the inbound calls via the relevant channels and its cost, with a total of it. The CORE should be something sturdy, with data saved in a database. Opensource CORE is welcome. Either Kamailio, A2B, FreeSwitch, Kazoo, or any other robust switch and billing system. There is NO outbound VoIP in this switch, its purely inbound. Ultimately, we need to know which provider is calling our DIDs, and we need to allocate a cost so we can bill them for sending calls to us. We need someone with good experience to handle this project. Tx Mo