I cannot answer your question; however, my understanding is that in the case of voluntarily relinquishing your seat, you are not entitled to a refund, but rather compensation in the form of vouchers for future travel and a confirmed seat on the next available flight, even if that means endorsing your ticket to a different carrier.

It is my understanding that you are only entitled to a refund in the case of involuntarily being denied boarding.

Does anyone know if this is correct?