When a call center person asks if I've had a particular problem that's causing me to cancel, I say no.
When they suggest that they might be able to help, or in any stall with canceling, I tell them I've changed my mind and now I have a problem with their customer service.
It probably depends on if you've got one of the reps who's worried about being fired because they've gotten too many "I want to cancel" calls. It's not unusual for call centers to 'motivate' their employees in that manner.
I think it really depends. Sometimes you get a call center rep who doesn't really fight you on it, sometimes it's incredibly frustrating.
Cheers!