In one sentence, describe what the following article is about:

When calling a mobile phone in Hong Kong, you must still enter the international access code for the U.S.  To do so, dial 011 on your phone’s keypad. Hong Kong’s country code must be entered as well.  Use your phone’s keypad to enter 852. Cell phones in Hong Kong begin with an area code of either 5, 6, or 9, depending on the mobile carrier.  Enter this number using your phone’s keypad.  Dial 00 to reach an international operator if you need help determining the correct mobile area code for a specific Hong Kong wireless carrier. Because of the rapidly growing population of Hong Kong, mobile carriers are starting to use the area codes 4 and 7 as well. Next, enter the 8-digit mobile number using your phone’s keypad. After you have entered the international access code, country code, mobile area code, and mobile number, press send to place your call. If you are calling from a mobile phone and your call does not go through after entering all the information above, try adding a plus sign (+) before the mobile area code.
Dial 011. Dial 852. Enter the mobile area code. Dial the mobile number. Press send.