CANCELLATION does not WORK

I remember I signed up for a free trial of Acrobat Pro just to use it once, and then later cancelled the plan. I wasn't sure that I needed to receive a cancellation confirmation email, so I just shut down my computer and went on with what I was doing. I was even sure that I cancelled because I wasn't able to access all features on the app itself when I went back to it.
Fast forward few months later, I realised I was being charged for the subscription to my horror. I contacted support but they could not do much. No refunds were given, even when that was the ONLY time I used the Adobe Acrobat Pro. This was so distressing. If I ever forget to cancel again on March, since this is a annual commitment plan, I would have to go through the whole cycle again, just giving my money because there would be a cancellation fee.