Not sure if this should be on the Iberia or British Airways forum.

Recently flew London to Barcelona on IB coded basic economy flight I purchased on Iberia's website. Flight was operated by BA so I had to check in with BA. I'm Oneworld Sapphire (AA Platinum). I had one checked luggage. Thought OW sapphire was allowed one free checked luggage on basic economy flights in addition to one carry on. At the airport in London, BA refused to allow my checked luggage without paying for it (almost $80). Back and forth ensued with agent then a supervisor arrogantly saying luggage does not fly without payment. I called Iberia and they said as OW Sapphire, I was entitled to one free luggage. Because I needed to meet up with friends in Barcelona and did not want to miss flight, I reluctantly paid the baggage fee with notion I'll request a refund later. Note, I had just arrived 3 hrs earlier on a BOS to LHR IB coded BA operated basic economy flight and did NOT pay for my checked luggage as a OW sapphire. Even my return from Madrid to Boston was also IB basic economy and I did not pay my checked luggage fees as well. The LHR to BCN was a separately purchased one way ticket.

So, on arrival in Barcelona from London, my luggage did not arrive. Stood in a long almost 3 hr long line to file a report for lost luggage. When I got to front of line, they said my luggage had been found and put on next flight from London that actually just arrived as I stood in line.

Now I'm back in the US from vacation, who (and how) do I make a claim to demand a refund of my $79 baggage fee? Iberia or BA? What other compensation am I entitled to, if any?