+1.UpperNwGuy wrote: ↑Mon Mar 20, 2023 11:22 am OP,
Welcome to the frustrations of booking travel to, from, and within Spain! This kind of problem (credit card being rejected) occurs frequently with both Iberia airlines and Renfe (the Spanish rail company). Your bank is not at fault. The fault is with the terrible websites of Iberia and Renfe.
It's not "Big Bank's" fault. It's Iberia. I've had the worst problems booking with Iberia & Renfe. I think the workaround for Renfe was using Paypal? I don't remember how I finally got my Iberia flights ticketed.