High download latency

Been having an issue since almost the start of this year with intermittent complete loss of internet and high latency/lag.

It got so bad that an automatic text was sent offering to have a tech come out to check things out so we opted to go ahead with it (back in April). The tech came out and checked all of our equipment, stating it was working perfectly fine and was reaching very high speeds, but also stated the issue may be the cables outside the building. Ever since then we've heard nothing, and there's been an xfinity work truck out there that same week maybe twice and still the issue persists. Can't even reach them by phone anymore. Went ahead and replaced both the modem and router (both of which were about 2 years old) and still the issue persists.

Anything I can do at this point? Far as I can tell, the chat functions down on my end and there's 0 troubleshooting surrounding this issue. Any test xfinity runs based on speed alone naturally shows everything is fine but it doesn't test for any latency or lag.

The issue remains across all devices, whether through a wired or wireless connection.  1200 mbs speeds mean nothing when latency is nearly as high in some cases

Considering how many years we've had xfinity and it's consistently had more problems than just about anything else....I'm already looking into other alternatives that have recently popped up in our area that would cost a fraction of what I pay now and still deliver nearly half the speed of what I pay for now...