How do I access my Jagex account linked to an unrecognized Apple email address?

I have an account with Jagex for RuneScape. I’m paying a subscription fee every month but when I contacted them to say their system doesn’t recognise any of my email addresses, they replied saying the account I was made using my Apple account and so they can’t help with any specifics and to contact the provider to try and resolve the issue. It’s super annoying and not very helpful, equally there is no way for me to contact Apple either so what do I do from here? Can’t cancel the subscription without logging into account and the Jagex launcher reckons my Apple email address has no account. Can’t see a way to resolve it and get into my account anywhere.

[Re-Titled by Moderator]