Can you describe the problem in more detail? As a general matter, if you cancel your membership it means you're canceling your subscription--it's the same thing, and your membership expires at the end of your subscription. But simply changing your membership, such as signing up for a longer subscription, wouldn't cancel it; it would extend it. Conversely, I doubt you can change a long subscription period to a shorter period and get a refund of the difference. Generally once you sign up for a membership, i.e., you subscribe for a certain period, you can't get a refund of your money if you're not happy with it. But I'm not sure exactly what your issue is.

change/ cancel membership will allow you to turn off your autorenewal and continue with the service for the remaining time without being charged at the end of your subsc. period.