Request a Refund
This website (musescore.org) has no payment/subscription service. You are likely talking about the Pro subscription of musescore.com (See What is the difference between MuseScore.org and MuseScore.com?).
They offer support for account and payment issues via email@example.com (8/24h 5/7d, regular business hours, Limassol/Zyprus time). You may also use the "Request a refund" button under "Contact us" link at the bottom of the musescore.com website.
But find more details at https://help.musescore.com/hc/en-us/articles/360012156839-Requesting-a-…-
Nobody here on musescore.org and its forums can help you with your request.
See also How and where to ask for support