Subscription by mistake

I have made a subscription to PicsArt: it was a mistake. PicsArt didn’t manage to take my money from the credit card because I had not enough money. I cancelled my renewal for the subscription immediately but I didn’t manage to cancel my subscription for this year and now I have this subscription without paying but I don’t want it. I can’t do anything now with my apple account because , obviously, I didn’t pay a subscription, but I want to cancel it. I contacted PicsArt but they told me that I have to talk with you to solve the problem, because PicsArt can’t do anything with my apple account. Help me!!