COX won't update customer provided modems after screwing up Gigablast speeds....

I do have the same issued, Cox never fix my problem, i'm been with cox almost ten years, this year is very bad services? they're send the technicians to my home, the guy just replace slitter and he left he's say it's good to go. I told him you has to look inside my modem MB8600 see error, but he keep say it should be good now, but after he left the issue are the same? Then called motorola, they're swap my modem and are the same issue? also most my friends with cox has the same issued?