Can't reach anyone to cancel my business service.

I have been trying to cancel the business service in my office for the last week. I have called 4 times on 4 different days. Every time I reach someone at Comcast, they say that the Disconnection Specialists (or whatever they are called) are all busy but that someone will call me back.

No one has returned my calls  I am getting frustrated trying to get someone to act on my disconnection so that billing will stop. 

Can someone help?