It is the business practice of sending all clients' billing info to a separate company, who then does everything for you. It also allows a company to cut down on time and human resources spent on administrative tasks.
A decade ago, call shops were the most convenient way for tourists and immigrants to contact their families. Today however, this has changed, the number of ways getting in touch with their families abroad has increased with the Internet, and currently it is threatening to the survival of the call shops.