BCN-BOS isn't Iberia, it's Level. So your Oneworld status is irrelevant, although I do recognise that you are aiming at this stage for rule-bending rather than elite benefits for your trip.

AFAIK, there is no "Oneworld Emerald" desk at Iberia. IB+ elites may have their own numbers to call, but AFAIK that only jumps any queues - not reach dedicated, more qualified and empowered agents.


Perhaps your better option is to use your voucher on a flight / fare that is fully refundable. Later on you cancel that dummy booking for a refund that would also come as a voucher, but hopefully with new expiry dates...