Looking into it, I found that I was being charged for internet services through 4/27. Apparently, even though they were scheduled to end on the 20th, and furthermore cut me off on the 11th, I'm supposed to pay for a full month.
Since billing services is only available on the phone during business hours, I dug up their email form, entered all my info, and wrote an only mildly scathing letter (In the end, I decided to forgo the "see you in hell" comment).
Which was rejected out of hand by their system because they didn't recognize the phone number that was cut off Friday.
A second click on "send" resulted in what appeared to be success, but I suspect actually meant the message was consigned to oblivion. If I don't hear anything by Monday afternoon, I'll go the phone route.