You can make and receive calls in Hong Kong through your mobile phone as long as it’s Dual Band, Tri Band, or Quad Band. Mobile operators in Hong Kong have partnerships with foreign operators, therefore you should ask your local operator first regarding the roaming rates, international calls and SMS rates that will be charged to you before departing for Hong Kong. Local SIM cards are available throughout Hong Kong, particularly in 7-eleven convenience stores and in tourist hotspots such as Central, and Tsim Sha Tsui. The average cost for a SIM card ranges from HK$48-HK$98 depending on the services and credits that come with the card (ex. 3g network, multimedia use, etc). International call rates range from HK$3.80 to HK$6.40 per minute depending on the country. Recharge/reload vouchers are available at 24 hours convenience stores. For more information on mobile rates, check the Office of Telecommunications Authority.
The country code of Hong Kong is 852 and there is no city code for Hong Kong.
It is more advisable though to just purchase a local phone chip/ SIM card once you’re already in Hong Kong, as it will allow you to make calls and SMS at cheaper rates.