Not SXM flights, but AA domestic flights that we (not AA) canceled. When we canceled them, we were told that we could call to rebook anytime before the end of 2020. Once I saw this thread, I went ahead and requested the refund online. It took about three weeks, (Correction: only eight days, lol. Just seemed like 3 weeks) but we received notice that our refunds would be applied to our credit card. One small downside, and I'm not sure I'm even going to worry about it, is that we had applied $300 in vouchers that we had gotten for severely delayed flights last year, and those were not reinstated. Added note: it's possible that AA actually canceled the flights after we canceled our tickets, as I did try to find them on Flight Aware, and couldn't. Not really sure if the flights flew or not, but we did get our money back.