Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Greetings!
This is Tin, I understand that you would like to cancel your subscription from your old account. Since you don't have access with your old account, have you tried to reset your password there? If you still unable to access it even trying to reset the password, it would be best to reach MS Accounts & Billing to cancel it for you.
Kindly open this link: https://support.microsoft.com/contactus/
Ensure that your MS Account has been signed in
Type "Chat with an agent" and hit Enter.
Please click the "Contact support"
Please select the "Products and services"
Please follow the prompts to connect with a live agent.
You may also choose the "Call me back" option if you prefer to receive a call.
Once you're connected to the Live Agent, please let them know about your issue so they could check your account and address your concern.
Thank you,
Christine