How to cancel Slowly Plus

I've been using Slowly for two years now so I thought it would be good to sign up for a year, to pay for my use. I only wanted to sign up for one year, so I thought I'd cancel after I'd paid and it would just run for a year.

I signed up on my laptop, but I can't cancel! My phone says I need to do it on my laptop, and the laptop app won't let me cancel. I can see the link to cancel, and the link to change method of payment. I can click on the latter but not the former! Does anyone know what to do about it? Can I cancel before next year? I don't want to be billed automatically for another year.