Hello Marine Dawg,
Welcome to Microsoft Community.
We may not have great advice on this, because what I can tell you is that the Surface Duo could work on AT&T, T-Mobile, and Verizon Wireless networks.
But if the issue involves number sharing, it's a question of whether the carrier can provide the service, not whether the Surface Duo 2 can do so.
In other words, if your carrier tells you they can't do this, it means your number can't be used on multiple devices at the same time.
Best Regards,
Mitchell | Microsoft Community Support Specialist