Inphonex outgoing DID

My provider is Inphonex.
I have 2 Virtual Numbers (VNs) assigned to 2 DIDs.
VN 1234567 is assigned to 8551234567
VN 7654321 is assigned to 7637654321

When a call comes in on the system, Inphonex sends the virtual number, therefore to route the call based on DID dialed I have to have separate VNs.
I have a single trunk set up and I register both numbers.

Incoming calls work fine and are routed as I expect with calls coming to the 855 number going to the proper place, and calls coming to the 763 number going to their proper place.

The problem is that every call I place shows the CID for the 855 number and no matter what I try I cannot seem to get the CID for the 763 number.

Has anyone attempted to do this with Inphonex and can point me in the right direction?

Every trunk provider does things differently, however, normally the CID is determined by the CID sent to the provider by the customer. This can bedone in several ways, define it on the trunk or on the outbound route or on the extension, so it can be trunk, route or extension dependent. If nothing is sent the provider normally inserts a default. Most providers examine the CID sent to ensure it belongs to the customer and insert a default if its not while others let the customer send whatever he likes.

Right, I understand how the CID works. I was wondering if anyone has any experience specifically with Inphonex as setting the CID at the route or extension level is not working, and I only have the single trunk.
Inphonex provides no direct support for Asterisk, just their Knowledge Base which does not address this issue.

I tried creating a separate trunk which allowed me to get the proper outgoing CID but with 2 trunks on the same account, incoming calls were not getting through.