I'm assuming you are speaking of Lan Kwai Fong?( Lot's of Westerners?) I can't say for myself as I have never partaken, but I have heard that there are 'working' girls available in the bars on D'Aguillar Street....I guess kind of like Wanchai.
Does your phone number show up when you call other people. I've seen that some of the HG ads state that you need an unblocked phone number, that way they can weed out people who are just wasting their time. I know in San Francisco that most apartment massage parlors/escorts will not answer calls from blocked numbers.
As to what to say, it all depends if you speak Cantonese/Mandarin or not
? Basically let them know who you want to see, and at what time. Unless you know the papsan pretty well, you can only schedule a session on the same day/night in which you call.
Hope that helps a bit. Maybe the more seasoned bros can chime in as well.