The Ponsonby girls are good but it depends which one you get. I can recommend the little Asian Sammi. Although not working today. She was genuinely early 20s.
Some of their ads seem to be the same women using multiple personas. It's run out of a couple of private apartments. When you arrive at the street they make you stand on the street corner so they can view you which is bit of a hassle.
I think they do it just to make sure you're not a problematic customer/stalker. But would be interested to push some old 90 year old geyser in a wheelchair up there to see if they still accept his booking