If you’re staying in Hong Kong for more than a week, or if you have friends in the city, it’s certainly worthwhile getting a Hong Kong sim card for your mobile phone. Although you can set-up roaming with your home network before you leave your home country, this will prove far more costly.
A Hong Kong sim card will allow you to make cheap calls in Hong Kong, as well receive calls from abroad, without it causing a fortune, although you will still be charged.
You can purchase a card from any of the cities 7-Elevens, however cards purchased there have proven consistently unreliable, and it is better to seek out a Smartone-Vodaphone shop and purchase one there.
Cards are priced at $15, the cost of which you will receive on the sim card. Simply remove your home sim card and replace it with the Hong Kong sim card to use. You will receive a Hong Kong phone number on which you can be contacted, this should be on the information you receive with the card.
If you need more credit on the card, you can buy more in denominations of HK$50 at 7-Elevens or Vodaphone shops.
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