FYI, no need to call in. I very recently (in the past 10 days) had this exact thing happen--outbound non-stop changed to connecting. Requested the refund online at prefunds.aa.com and the system recognized we were due a refund based on the applicable rules--gave us the option of refund to payment credit card or flight credit (plus a bonus, I think, but may be mis-remembering). It was pretty quick, too--6 business days between requesting the refund and notification it was approved/complete (hasn't posted to the credit card yet, but expect to see it by end of this week).

Be aware there are different rules/thresholds applicable to tickets purchased before April 8, 2020 and those purchased on/after April 8, 2020; available here.

cheers!