That's fairly easy to deal with. Answer every question, argument, and pitch from the representative with "please cancel my subscription".
That gets 'em through their script faster.
I have expressed in no unclear terms that I want to cancel my subscription and I don't want to answer any further non-essential questions about it. Any further questions that are not legally necessary to terminate our relationship will be considered usage of my professional consulting services at the rate of 10$/minute for which I will send you a bill after the call finishes. How may we proceed?
I'd love to know what would happen next.
That said you might have certain consumer protections you're not aware of. I had cell phone plan with Comviq here in Sweden that I wanted to cancel and they said on their website that I needed to call. Swedish law requires my being able to cancel in various ways (e.g. sending a letter, or sending an email, etc.) regardless of what they said in their initial contract. So I found an address and just sent them an email stating I wanted to cancel. In a day or two it was done. I presume they know they are legally required to do so and so they did what I said, but I'm also sure they happy to provide conflicting information making consumers unaware of their rights. I reported their website to our consumer protection authorities, but I never heard back.