That completely depends on which class (Blue discount Economy, full Economy, or Premium Economy) you're booked in and the associated charges.

If booked with Iberia Avios, you should go through IB.

A quick dummy booking suggests the standard rates Iberia use apply, so a refund+cancellation costs 25 euros or 40 USD per leg in Blue Class and Premium Economy and no charge in full Economy. In discount and full economy, it must be done 24 hours or more before the first flight; this doesn't apply in premium economy and it's just any time before departure of first flight.