I bought a new iPhone and AppleCare with it, but my old iPhone's AppleCare is still active til Nov. 28, 2022. Can I get a pro-rated refund?

Cancel or change the payment method for your AppleCare plan - Apple Support

If you cancel your AppleCare plan more than 30 days after your purchase, you’ll get a refund based on the percentage of unexpired AppleCare plan coverage, minus the value of any service already provided.1

1. The refund guidelines might vary in your country, region, state, or province. You can find more information about canceling and refunds in the applicable AppleCare Terms and Conditions. If you pay monthly for AppleCare+ from your wireless carrier, contact the wireless carrier to request a refund.

I had that happen once and I got a refund. I suggest that you contact Apple directly by clicking on Get Support at upper right corner of any forum page.