I’m not sure if this is possible, or if I’m approaching it correctly. I’m trying to originate outbound calls over a BYO SIP trunk while dynamically specifying the caller ID at the time the call is created. The SIP trunk and credentials are already set up and working properly. However, we need to place outbound calls using different numbers that we own. It doesn’t seem practical to provision a separate phone number resource for every outbound caller ID we may want to use. Is there a supported way to dynamically set the caller ID for outbound calls on a BYO SIP trunk? If not, is it possible to pass a custom SIP header (for example, an X-header) that we could rewrite on our SIP server to control the From header before the call is sent upstream?

@falseVacuum the I want every caller ID I own without provisioning 50 lines move, most sip providers lock you down unless you do some header gymnastics. you can often rewrite from via an x-header on your sip server, but push too hard and you’ll end up in spam jail faster than you can say dynamic cid.

@Lékè ~ Wyzê We are an SPC-authorized provider and we sign our own outbound calls. Like most VoIP providers, we are able use any caller ID we have authority over for outbound caller ID.

@falseVacuum If you’re spc authorized and signing your own calls, the carrier isn’t the bottleneck, the platform is. Most systems quietly override from / pai at the trunk or auth level even when you think it’s dynamic. That’s usually where the we can send any Cid story falls apart.

@Lékè ~ Wyzê I think we may be talking past each other. This isn’t a carrier restriction issue. We’re an SPC-authorized provider and sign our own outbound calls, so we can legally originate using any caller ID we have authority over. My question is specifically about VAPI’s outbound call API behavior. I want to originate a call from a VAPI assistant over our BYO SIP trunk, but dynamically specify the From caller ID at call creation time (based on which customer the call belongs to). Right now, the only supported method appears to be creating a BYO SIP trunk as a phone number resource per caller ID. That doesn’t scale for us - we have hundreds of customer CIDs. What I’m trying to determine is: • Is there a supported way to dynamically set the From header when creating an outbound call over a BYO SIP trunk? • If not, is there a supported way to pass a custom SIP header (e.g., X-Customer-CID) that we can rewrite on our SIP infrastructure before sending upstream? The core issue is platform flexibility.

this is purely about vapi outbound Api, not carrier rules. From what I’ve seen, vapi typically binds the from to the phone number/trunk resource and doesn’t expose per-call header overrides on Byo trunks. If that’s the case, dynamic Cid at call creation probably isn’t supported natively. Unless they allow custom Sip headers in the outbound payload, the only scalable workaround would be inserting your own Sip proxy to rewrite from before it goes upstream.

Brother. I don't think you understand this stuff. I'm originating to MY OWN SIP PROXY. That is litterally what I'm saying.

We don't allow adding the caller ID field dynamically. You can add a phone number via API, and you can reuse the credentials. So you just need to create multiple phone numbers via API that use the same credentials For outbound calls, we don't give the option to edit the header.

@Sarthak thank you for the clarification