Just put it on the CV you apply with. If they ask, you can say it wasn't relevant to a reservations job (it's really not, aside from the generic "customer service" aspect, which I assume you already had from some other job to be accepted into reservations/ticketing in the first place)
They really don't care, since they train you their own way. So long as you can explain it, will be a non-issue in my opinion....