Constant Cutting In and Out

I have been having the same issue since 12/13, so over a month now. The wifi constantly cuts in and out every few minutes. We have already had three techs come out and try to address the problem, once on Friday, 1/3, once Wednesday 1/8, and once Saturday 1/11.
The technician Wednesday replaced the gateway with a new one yesterday, as well as ran all new lines. He said that the speed going into the modem was great, but the speed coming out of the modem was terrible on his system that he used to test it as well as on my devices. This did not change after he switched out the modem. Before he left, it seemed like it was fixed, but a couple hours after the appointment, the wifi started doing the same thing - cutting in and out again. (To be clear, my tech did everything he could possibly do and I was very happy with his performance, this is a network issue, not a technician issue.)
I pay for 500mbps and am only getting between 40-70 every time I run a speed test through the app and through a third party app, with the wifi constantly cutting in and out.
Because I work from home, my job quite literally depends on the internet, so this is completely unacceptable. The reason I pay for high speeds is because I need high speeds for my job. 
The issue was escalated to maintenance Saturday the 11th, with the maintenance man coming to check various points around the area. I received a text that the work was finished and that our service should be back on with no interruptions. This was not the case, the service is continuing to drop every few minutes. 
What needs to be done next? The techs obviously cannot do anything more, and it seems like this is an xFinity network issue that does not stem from my home. It does not feel like we are any closer to resolving this issue.  Do I just need to cancel and go to a different provider? I cannot continue to pay for wifi that simply does not work.