How to actually get in contact with customer support?

My credentials were compromised, but I have now secured the account. I am experiencing ongoing mailbox compromise/persistence. Malicious rules were created that forwarded specific emails to an external Gmail address. The rules continued appearing after I changed the password, enabled 2FA/passkey and signed out all sessions. I have no active forwarding and no authorised third-party applications. I am still receiving QuickMailChecker/SkyMarket and Ninhomail messages which block actual emails incoming. I need the Outlook.com mailbox investigated for hidden/server-side rules or other persistence. When trying to access Outlook support I'm met with a loop that just takes me back to sign in with no further action.