Internet speed not even close to advertised

I will try to make this short. First off we have brand new state of the art equipment and I am pretty knowledgeable on setting up at network and how internet works.

We started our plan with the “up to” 300mbps, which I know is an “up to” and not always guaranteed. We never got over 100 mbps wired or wireless.

So we had a tech come out and checked over everything and he states everything is working the way it should.

Fast forward a couple months and we opted for a promotion to get up to 600 mbps download at the same price.

Our speeds went up to roughly 200-250mbps respectively.

Fast forward another couple of months and here we are today. For the last few days we can’t get more than 22mpbs download and 8 upload. Almost as if we are being throttled.

We pay for unlimited data. I’ve done everything under the sun.

Reset all equipment and devices, changed dns servers, tried using a reputable vpn.

All year across any speed test site, ookla, Comcast, google etc.

Yield the same results.

Comcast is of no help as they state that nothing appears to be wrong on their end. Any help would be appreciated