Non refundable flight

Ok… just a quick question for anyone that’s done it, I Got 3 seats for a flight, it’s non refundable, one of us can’t make it but I see if we cancel we can get credit for new tickets, but when about about to cancel I see it says must be used with same passengers, do you have to get tickets for all three passengers or can you use the credit for 1 or 2 tickets? Thanksssss