Asked for new ip, said my ip was bogon!

Not only does the modem get assigned a 10.x.x.x IP for diagnostics but Cox(and other ISP) uses the 10.x.x.x space for routing too. AKA you will see it in a tracert.

As for how to get a new IP address, what model router do you have? If the router has something called MAC cloning you can change your WAN MAC and then reboot the modem for a new public IP. If you have a Cox Panoramic gateway you are out of luck I think. The only way to change the IP is to get a whole new gateway. 

I've got a netgear CM1000v2. Trying to find out how to do it there.

The netgear isn't going to get a routable IP address, it's going to get an internal COX ip address starting with 10.

CM1000v2 is your modem. What model router do you have?

I have a Google Nest.

It's the ROUTER connected to the netgear that gets the WAN ip address. the Replace the router, or change the MAC ID of the router. 

You mean my Google Nest? That determines my public ip? I just installed that a year ago and my public ip didn't change. How do I do this on Nest?

the T1 agent cannot give you a new IP address. The way to get a new IP is to change the mac ID of the equipment connected to the modem, or change the router connected to the modem. That, or remove the router from the modem and connect your computer direct for a couple of days, then when you reconnect the router back to the modem, your old address should have been assigned to someone else, meaning you will get a new IP address.

Doesn't look like it is possible with the Nest line. Sorry.

Isn't there a trick where you can deprovision someone's modem, locking it with a 172.x.x.x IP, then re-provision for a new IP address? I know it used to work before but that was when provisioning was local to the CMTS. Now it seems like a modem will work on any node, not just the one it is assigned to.