Not Getting Gig speeds On New Service

A week ago I switched from preferred to Gigablast for better service. My speeds sometimes have gotten faster, as high as 340/36 but it’s not acting like it. My TV is constantly dropping Netflix and Disney plus. 

I am running a NEW SB8200 Arris coupled with a NetGear Nighthawk R6400. Speeds are using WiFi on my IPhone XR. I tried to call and do the live chat but just sat in queue for hours.