Comcast won't cancel our service!

I was unhappy with Comcast and switched over to RCN starting June 20 (along with our phone number). On the day that our service was switched over, I returned all the equipment and called Comcast to cancel our service.

To my surprise, Comcast would not cancel our service, saying that there is a "open work order" on the account. It has been 3 weeks now and there is still a work order on it and we are unable to cancel, while getting billed for the service. Although Comcast says that they will predate the service end date so that we will not be charged, on paper I am still being charged. I don't want to pay but am worried about it affecting my credit score. (I am guessing this is why they are doing this!)

I don't know why I cannot just cancel my service since I am not the one requesting anything requiring a work order.

Ridiculous!!