You can contact MuseScore Customer Service at support@musescore.com. They will reply to you within 24 hours or faster.

YOU CAN'T - IT'S ALL AUTOMATED UNTIL YOU GET MONEY TAKEN OUT OF YOUR BANK ACCOUNT, THEN POST A COMPLAINT AND THEN GET A LOOOOOOOOONG WINDED "REPLY"

Nearly impossible. They have ridiculously short office hours, take days to respond via email, and have no phone number for contact.

They respond but are entirely unhelpful to requests for subscription cancellation or refund

They answer emails with completely unhelpful responses.

They responded to my email within an hour of sending it

Hi, thanks for the question! It's much easier than you think. For any inquiries, you can contact us via support@musescore.com. We'd be happy to help you!