Hi Tonice and welcome to the board.
The phone thread had RA20 on it not because phone technology is top secret in HK
but merely because we like to keep some of our personal stories discreet from time to time.
You will of course be needing a local mongering phone in order to find the girls in order to write reports on the girls
so let me help you out with what little I know. I'm still figuring out the HK phone thing myself and I don't think anyone has it all nailed
yet.
First off, HK has telephone interchange agreements with many of the international carriers in the world (ATT in the U.S. for example) and, while not ideal, it is possible to get a $6.00/month calling discount plan with some of those carriers that will cut your cost per minute down considerably (like in half or better). Also, at least with my U.S. phone, I get charged the same for an SMS ($0.20) whether it's in HK or Timbuktu. This is important since you can do a lot of booking by SMS rather than voice and avoid many of the language hassles in HK.
I am NOT advocating sticking with your home phone to book hookers. I'm just saying that it's worth checking the cost of these things and maybe your home phone will be an affordable backup. By far the best way to go is to bring an old phone with you, and buy a local SIM chip at the 7-11 and then add top up minutes as you go. This way you will be able to phone internationally for as little as $0.10/minute. You should buy your SIM and get TWO top up cards and immediately load up one of the cards, keeping the spare in your wallet for when you run out at 1 a.m.
When you buy the top up card the checkout staff at the 7-11 are so nice they will even load up the minutes for you.
For services I've used PCCW (roaming) and CSL (pay as you go) and both have had fine coverage. I've asked on the board before if there was a service that was better for roaming (cost-wise) and nobody really knows. It's phone bills, they're a mystery in any language!
As to a pay-as-you-go card that will roam in both HK and China, I do not know the answer. Perhaps one of the senior bros and old China hands can help out.
Thanks for your interest in joining the brethren here. You will have a mind-blowing time in HK. I look forward to your reports!