Trying to cancel my subscription but I have no plans on my account so I can't

I was signed up to a plan as part of a module in college where it was charging me €19.66 per month. I then tried to cancel it once i had finished this module but i was going to be charged the rest of the years worth of monthly payments, so I had just left it. A few weeks ago I tried to cancel my subscription as the year had been up, but no plans are appearing when i go to "Manage My Account" and customer care is telling me that only my administrator has power to ask any queries, I was then charged €30 for the month of February yet i dont have access and cant cancel my plan. I really need to get out of this plan as i have spent just over €250 on this app in the last year yet i only used it for 10 weeks of that year. They have not given me any help at all on this issue and I am in desperate need to get out of this subscription, I cannot pay €30 a month now that i am no longer in a student account and no longer need this app. Any help would be really greatly appreciated, thank you!