The second-worst experience I had with cancelling a service was with Comcast. Briefly: called up, told operator I wanted to cancel, they put me through to a special sales team attempting to keep me, eventually I pushed it through.
The real magic happens during the conversation with the sales rep; he asks why I want to cancel, I explain that the cost is high relative to the quality. He offers me more cost effective package, I explained that I had that package in the past and that the slow incremental increases in cost had turned me off them as a company. He goes on to say: "well, that is your fault, I'd never set up auto pay for a service" and continues to make the case that the convenience function of auto pay is actually an agreement with Comcast to increment the cost of my service without my explicit agreement to paying more.
Wow. Just wow.
Still, that's nothing compared to the calls I had with BT after someone hijacked my landline and placed hundreds of GBP worth of calls to Nigeria... but that is another tale for another HN story.