I also am only getting 300Mbps down and 250Mbps up. I was originally getting around 250Mbps down and 150Mbps up. Personally I think it's more promotional, since they have so many qualifiers of why you may not be getting the desired speed.
I think the speed increase was mostly for cable(HFC) customers. If your getting 250Mbps up, you must be fiber. Did you get notification of your speeds changing?
Yes, I received an email from Cox a few days ago. We are on fiber.
Have you tested direct to the ONT? If so, I would email Cox at cox.help@cox.com and see if your circuit is rated for 500Mbps. Not sure how it works with fiber but maybe something on the backend has to be refreshed with the change.
