Why won't Comcast Business won't let me cancel my service?

I've been trying to cancel my service for almost 3 weeks now - phone number is either never answered, or I'm told I'll get a call back that never comes, or I actually get an email from a rep who promises to help and then is never heard from again (and never replies to my emails).

This is the latest in a string of service failures: since the start of this year, Comcast Business and Xfinity residential service techs have been to my house 6 times. They have confirmed that there is a massive signal drop-off at the front wall, but have done nothing to fix it. They replaced the outside cable, located and shut-down all but one internal outlet, replaced modems and other equipment and put 'filters' on my equipment. As a result, nothing has changed except that I now have a large spool of cable at the bottom of my driveway, because the tech didn't have the equipment to run it up. 

To be clear, I have tried for six months to fix the problem of my service dropping out multiple times an hour (either completely, or to such a degree that I cannot run my business). Meetings with clients on zoom or teams are awful, file transfers fail constantly, the wi-fi craps out all the time, and we can't even log in to our own server. 

In addition I've been told by two techs that the problem was probably a damaged cable. But they refuse to repair or replace the cable we have. In fact that last appointment a tech never even showed up, and when I contacted an agent and they reinstated the appointment and promised a Senior Tech ... no one came that time either, leaving me waiting around all afternoon (twice) for someone who never even bothered to show up. 

To say that this experience has been dismal is a huge understatement: my company pays hundreds and hundreds of dollars to you each month, and at every turn when we needed you to actually do something to help us, you have turned your back. 

And now, you're refusing to even process a service cancellation. Please cancel my service. I don't want to have to devote an undue amount of time to this process, and certainly don't want to go down the route of gathering all the complaints here and elsewhere as part of a formal move to bring attention to what seems an all too common challenge.