That isn't how employment contracts work. They aren't obligated to work for free or for whatever they are given because there is a hardship somewhere in the world. There is always somewhere a volunteer is needed. You are essentially arguing that their wages should be shitty and they should HAVE TO work because you volunteered your time to a rescue effort. Why aren't your complaints aimed at those withholding higher wages? It would be as easy as a push of a button for them? Why aren't those corporations responsible for the hurricane like the wage slaves?
That there is a need somewhere does not entitle you to anyone's labor.