So I have a return flight MEX-Mad in, ay next month and aim struggling to make head or tail of their seat selection policy.

Firstly, they say if I pay for a seat now I can't change it again until online check in, which seems crazy and means there's absolutely no point me paying for a seat before then when I don't know how the seat map will look on departure day so can't make an informed decision.

So what I want to know is, with Iberia can you go to online check-in, see the seat it has assigned you, and then choose to purchase a seat? And if you purchase a seat then can you change this seat after that, before getting your boarding pass or do you get one shot and that's it? I guess ideally I'd see what they assign me, and then pay for a seat later in the check in period when I see where the more empty rows are (I. E. increasing my likelihood of an empty seat next to me)

Overall, seems a pretty ridiculous system, I cannot understand the logic behind not letting you change a seat assignment between paying for it and check in.

Thanks for any tips.