This Forum is just a user to user forum, no-one here has any account access, you will need to contact Microsoft Support directly, they will be able to change your Microsoft 365 subscription to the Classic version without Copilot and provide you with a refund, try using this method to contact their support.
Go to this link: https://support.microsoft.com/contactus
Select Microsoft 365
Click 'Get Home Support'.
In the box provided, type billing.
Press Enter, then on the next page, scroll down and click 'Sign in to Contact Support'.
Navigate to Microsoft 365 and Office - Manage my Subscription.
Select the 'Chat with support agent in web browser' option