If you're coming to Hong Kong and want to use your mobile phone to make calls and text locally, there are many ways you can keep the costs down, whether you choose to stick with your home service provider or purchase a local SIM card. Alternatively, consider using free apps like Whatsapp or Viber, since Wi-Fi is widely available in public locations in Hong Kong.
If you are in Hong Kong for just a few days and only want your phone to make local calls, you can also consider using public phones. Local landline calls are free in Hong Kong, as well as in most shops, hotels, and restaurants.
If you want to use your own phone and number in Hong Kong, you'll be able to do so straight off the plane. But it won't be cheap. How much you pay for roaming or international network charges depends on which country you are coming from. Costs for calls can range from $0.1 to $2 a minute, but remember you'll also pay to receive incoming calls, but roaming charges for the data you use abroad are what you really have to worry about. Before you leave the country, you should check to see what your provider's roaming rates are like.
Free Roaming on Your Cell Phone
The good news is that some international networks are now doing away with roaming charges and higher international prices completely. That means you can use your free contract minutes and data in Hong Kong or pay the same price for calls and data that you'd pay at home. Currently, mobile service providers like T-Mobile and Sprint offer unlimited international texting and data plans for customers that live in the US.
Purchase a SIM Card
If you can't get free roaming and don't have Whatsapp or Viber, the cheapest way to stay in touch in Hong Kong is by buying and using a local SIM card in your phone. This lets you use local rates for phone calls and data. It does mean you'll have a different number during the duration of your stay.
To use a local SIM card, you'll need a phone that is unlocked (not restricted to use on your network only). Your home network will be able to advise you if this is the case. If your phone is locked, you'll need to get it unlocked at a mobile phone shop first.
Once in Hong Kong, it's easy to pick up a SIM card from any of the major networks. Hong Kong's biggest network is China Mobile, followed by 3, CSL, PCCW Mobile, and SmartTone Vodaphone. You can buy a sim card from any of the dozens of mobile phone shops around the city, convenience stores, or even at the airport. It will only cost a couple of dollars and a small amount of credit will usually be preloaded with the SIM card, but it's a good idea to buy more credit. All networks come with English language instructions for registration, and many have free bundles that offer cheap international calls if you want to call home. Receiving calls will be free.
Rent a SIM Card
Another option is to rent a local SIM card from the Hong Kong tourism board. These prepaid cards offer good value and are available for 5-day and 8-day periods. They include bundles of mobile data, low-cost international rates, and access to thousands of local wifi hotspots. Local voice calls are free. The cards can be picked up at 7-Elevens, Circle K's, at the airport, or in the city.