This type of scam was especially popular in the late '80s to early '90s in the United States before tougher regulations on the 900 number business forced many of these businesses to close.
A 1-900 telephone number, in the North American Numbering Plan, has the form 1-900-###-####, and is often called a 900 number or a 1-900 number ("one-nine-hundred").
Diplomatic services, such as the US Embassy in London or the UK Embassy in Washington, have also charged premium rates for calls from the general public.
In many European countries, for example France, Germany and the United Kingdom, it was common for organisations to operate customer service lines on premium-rate numbers using prefixes that fall outside the scope of the country's premium-rate number regulations.
The number used for the radio program was one that was specially arranged by AT&T Corporation, CBS Radio, and the White House, to be free to the calling party.