If you are traveling to Hong Kong just for few days and you are looking for Internet. I would recommend you purchase one2free 3G prepaid phone card. It cost only HK88 dollars and you will have 7 days unlimited Internet.
Where to buy the one2free 3G prepaid phone card:
1. After you have left the immigration and arrived in Hong Kong airport, take the Elevator and go up to the departure floor. 2. Then look for F corridor, at the end of the F corridor, you will see below 1010 shop. This is the place you can get the phone card after you get off the plane. 
They have two plan, one is $100 and the other one is $88. For both plan, after you purchase, $78 dollars will be charged for Internet service, the rest of the value you can use to dial any calls in Hong Kong. Choose any plan you wanted. 
At the back of the package, it tells you recharge methods if needed. 
When you buy at this counter, the customer service will assist you install the sim-card too. 
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