dropping internet

My internet has been dropping in and out over the past couple of weeks. I notice the issue mainly when I'm playing game that require the internet but I've also noticed it when streaming, listening to music and other things. I've contacted xfinity customer service multiple times and a a technician has come to my home and explained that the issue is not my modem or where it connects to outside but the issues is coming from the "tap" the green box in the back of my home. The tech schedules maintenance to come and fix the problem. I get a text saying the problem has been resolved... but that is simply not the case. I have contacted xfinity multiple times, had multiple techs and maintenance come to my house and claim the issue is resolved and nothing changes. I have become extremely frustrated with my ISP.