Hi, I'm John! I will help you with this.
Microsoft Q&A is public, and we can only provide information. It is beyond our capability to assist directly with billing or refund-related concerns.
To switch back to the Classic Microsoft 365 plan (without Copilot AI), please sign in to your Microsoft account "Services and Subscription" https://account.microsoft.com/services and select "Manage" next to your Microsoft 365 subscription. Choose "Cancel subscription", and when you scroll down, you should see an option to switch to the Classic plan instead. Just follow the on-screen steps to complete the switch.
If the payment was made recently (like the one on October 14), you can also request a refund through the same page by selecting View your options after cancellation.
I really hope this information is helpful! Let me know if you have any further questions or concerns.
Regards,
John J.D.