I had a look at the only published S r/t fare that is current on that route SR14C50N;
It says the fare is non refundable
It says that changes are USD50 for reissue and that it can be applied to a new ticket
and the only exception listed of note is that a refund in the form of a transportation voucher is available in the case of death of passenger,immediate family member or a travelling companion ( death certificate must be provided )
If you have that fare, looks like you can change for USD50, but no refund
Dave