Sorry to hear about your experience. If you look at HP's contract of carriage, Rule 240, this is a schedule irregularity. They are not required to refund you the amount you paid WN. That was your choice to fly WN. They do have to refund you the unused portion of your HP ticket. Now if they are offering you $200 vouchers in addition to refunding you the unused portion of the ticket, then that's about as good as you are going to get. They will not refund your whole HP ticket as you used part of it.