What exactly does "partially used" mean in this case? Can you give us the breakdown of segments, fare basis codes and what wasused/unused? For example(s) a ticket from ORD-SFO-BKK with the ORD-SFO used, priced as a single entity is considered wholly used, as it is a single entity. Also a refundable fare combined with a non-refunable fare, many tmes, becomes wholly non-refundable.
Without details, the question cannot be answered.