I got my Comcast bill in the mail on Saturday. Often I don't open bills because I do most payments online, but I opened this one. I noticed I was being charged $15.99 a month for HBO, something I don't recall ever having ordered.
After some checking, it appears the charges started back on June 2nd, the day I called to change my cable plan to one that cost less. The HBO was free for three months from that day, so after seeing the amount on the next bill in July was lower, I didn't pay much attention. I guess I didn't actually look at either the printed bill or the online bill for the details. Not a good idea, obviously.
After calling up enough bills online to see just what had happened, I gave Comcast a call and got connected to Steven. I told him I didn't recall ordering HBO. He confirmed to me when it had been added and the time I'd actually been billed for it. Then he said, "Let me do some math here." After a few clicking calculator sounds, he said the amount I'd been charged was $41 and some change and he'd credit that amount. He also explained that the current bill for the period which started yesterday would still include HBO, but the next bill would reflect the credit, including for the current bill. Also, he discontinued HBO.
It was that simple. I was prepared to argue, although it's not something I enjoy doing, so it's good it never came to that. I suppose it's possible back on June 2nd I'd gone along with an offer of three months of free HBO, in which case it would've been smart for me to note the date and cancel it before the three months were up. On the other hand, I was trying to reduce my bill, so saying yes to such an offer seems unlikely.
I'll be sure not to accept any such free offers in the future unless I'm prepared to pay for the service after that time is up.