CUCM Integration

I have a client that I’m trying to get moved to FreePBX. they’re a small office currently using Cisco Unified Communications Manager (CUCM). I need to temporarily have their calls pass through FreePBX as it it were a proxy, so I can slowly migrate each department at a time without taking everything offline.

I tried adding trunks in both CUCM and FreePBX (pointing to each other), however I cannot get outgoing calls to go through, and CUCM says “No Service” and I get no logs in FreePBX.