Internet disconnecting constantly and frequently

I have had the 600mb internet since moving in March of this year with my kids and the internet keeps disconnecting every couple minutes. I increased it from the 60mbps plan I had previously. I brought over the modem router, an arris surfboard SBG6900AC that’s working perfectly fine and supports up to 693 mbps. When we do a speed test the internet caps at ~65 mbps down, 15 up, for wifi and even for a wired connection. Unfortunately for the past three weeks the Internet connection has been disconnecting every so often. Every time I try to get help via chat it's like talking to a person that has no idea what's been going on and I have to go back to the very beginning and start telling them what I just told the person before them. I’ve gone through the manual troubleshooting procedure with multiple support agents this week and the disconnects have gotten to a point where the chat gets disconnected and I’m stuck in queue again to speak to another agent. This is beyond frustrating and I feel like every time I'm chasing my tail. There has to be a way to make a complaint further up the ladder instead of the normal chat and tells me he has done everything he can and leaves and the problem remains. Please if anyone has any ideas of how to move forward let me know. I do most of my work from home and need the internet to work, especially during client meetings and not keep costing me $$$ when it drops signal. We pay good money for the better internet speeds and you would think that the experience should match the fee.