A misdialed call or wrong number is a telephone call to an
incorrect telephone number. This may occur because the number
has been physically misdialled, the number is simply incorrect,
or because the area code or ownership of the number has changed.
In North America, toll-free numbers are a frequent source of
wrong numbers because they often have a history of prior
ownership. In the United Kingdom, many misdialled calls have
been due to public confusion over the dialling codes for some
areas. The recipient of a wrong number is usually unknown to the
caller. This aspect has been used in social science experiments
designed to study the willingness of people to help strangers,
and the extent to which this is affected by characteristics such
as race. This experimental method is known as the "wrong-number
technique". On a landline, wrong numbers are harmless to the
recipient other than the annoyance of answering an unwanted
call. But on a cellphone, if the plan charges minutes for
incoming calls, a wrong number ma