I doubt it can be used to offset your bill because from the description from the Rewards Catalogue, it reads as "Stay in touch with quality connections and extensive global coverage. Choose IDD 008 for clearly better premium quality or IDD 018 to enjoy smart savings and enjoy $20 worth of IDD talktime." Which, to my understanding, is you get to enjoy $20 worth of IDD calls to overseas friends.
## Love does not die because of distance. It dies because of doubt. ## Any views expressed here are explicitly to the best of my knowledge and sometimes in my personal opinion and not necessarily in the views by Starhub.