Yeah Vapi supports SIP trunking. You can connect it to your PBX by setting up a SIP trunk in Vapi and pointing your PBX extension to forward to it. The setup depends on which PBX you're running — FreePBX, 3CX, Asterisk, etc. all handle it a little differently. We deploy voice agents on Vapi, ElevenLabs, and Retell and deal with PBX integrations all the time. If you want to hop on a quick call we can walk you through the setup for your specific system. Call or dm we can help you!