When I was in Hong Kong twice last year, I bought a "3" card both times to use.
You can check out the information about this card here:
http://www.three.com.hk/website/temp...3b100&lang=eng

I'm not sure where to buy it but there are 3 stores located throughout HK and I found it at various shops (not sure about 7-11 and the like though because I didn't look there).
Text messages are a little expensive but the calls are cheap. The Government Mobile License & Administrative Fee also was not being charged at the time (but I'm not sure about now).

For International calls it was 50 cents Canadian which was quite reasonable and as I had the people call me back via Skype or some other VOIP service, I was able to get it down to 5 cents Canadian/minute (30 cents in Hong Kong dollar).

Right now there are bonuses on the cards:
Value : HK$98 – With extra $52 stored-value and totally $55 worth FREE multimedia usage upon card activation

So I think it's a good deal.

Good luck on your search.