Replaced Modem, Now internet speeds are 1/4th of previous speeds.
I recently had a modem that was fried from a lightning hit and the Cox store was awesome and replaced it with the exact same model, but now I'm seeing speeds of ~20 - 30 Mbps on fast.com, when previously I was seeing speeds of 120Mbps+. I'm on the 150Mbps plan.
What model modem, or gateway, is it? Are the speedtests wired or over WiFi? If WiFi, what speed are you getting wired directly to the modem?
A couple of thoughts, since your original modem wan fried by lightning, have you checked the cables for damage? What signal levels are you getting? Also, has your WiFi band or channel changed with the new modem / setup? To get 120 to 150 Mbps over WiFi, you must be using wireless ac on the 5GHz band.