I would first document the process with screenshots and video to prove you have failed to unsubscribe because of technical problems. Show multiple ways you trie

I would first document the process with screenshots and video to prove you have failed to unsubscribe because of technical problems. Show multiple ways you tried. Add further documentation by filing a ticket setting a deadline to get back your money, unsubscribe you and otherwise you will chargeback. If you can afford it: Contact a lawyer in case you may get sued and ask for instructions. Maybe he tells you to chargeback the money.