Changi Airport Group review: services

Upon landing at the terminal one Changi airport I needed to purchase a $15 Singtel phone card on 17th January at 8.30pm and was advised by the information centre staff to get one at the uob money changer.
Unfortunately when I went to the uob money changer there were 2 female staff who refused to accept my request. They just cut me off and said they are busy as they need to do a check and balance and shooed me away. When I said I really need one they directed me to starhub booth. This reaction of theirs can be checked on your cctv.
I was also unhappy because I only needed a $15 phone card for a week but the starhub booth staff had wanted me to buy a $30 card. I don't need a $30 as I am going to be here for more than 8days.
When I asked the starhub staff that I needed only a $15 call card I was told by the staff that he is 'unsure'. He was not helpful either.
This doesn't paint a good impression of a world class airport I was utterly disappointed with the reluctance of the two staff as well as the starhub staff who was trying to push a $30 card to me to make his sales.
Gowri