South Africa's telephone area code 054, or +27 54 in international format, is Upington, Northern Cape.
(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)
You will need to add the country code (27) for South Africa at the beginning of the number. Like: 1 + 27 + Area Code + phone number.
Country code +27 is South Africa. 027 or similar could also be a valid domestic telephone area code in several different countries.
The country code and area code of Kroonstad, South Africa is 27, (0)56.
The country code and area code of Bisho, South Africa is 27, (0)40.
The country code and area code of Welkom, South Africa is 27, (0)57.
The country code and area code of Middelburg, South Africa is 27, (0)13.
The country code and area code of Ladysmith, South Africa is 27, (0)36.
The country code and area code of Bethlehem, South Africa is 27, (0)58.
The country code and area code of Ermelo, South Africa is 27, (0)17.
The country code and area code of Humansdorp, South Africa is 27, (0)42.
The country code and area code of Kimberley, South Africa is 27, (0)53.
The country code and area code of Malmesbury, South Africa is 27, (0)22.