Unfortunately, the only way to cancel your service is by phone (866-347-3292). The reps here don't have the ability to do so.
My advice would be to keep trying. Maybe later at night, if you have that ability. Their call centers are very short staffed right now, and at the same time they're experiencing a large increase in call volume. A perfect storm, unfortunately.
Don't get me wrong, I know it's extremely frustrating not being able to get through, or even further, getting through, only to lose the call, and I really do wish there was some other way they could cancel your service, but to keep trying is the only advice I can give. :(
