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 may cost the subscriber one or more minutes.
Sources of misdialled calls are similar to sources of typographical error:
- Pressing one or more wrong keys on the keypad of the phone (example 2379 rather than 2349)
- Pressing a key on the dialpad more times than appears in succession in the phone number, thereby completing the length of the number prior to completing the intended number (example 7522-7 with the final 7 being ignored rather than 7527)
- Getting the digits in the phone number out of order (example 3416 rather than 3146)
Proper telephone etiquette recommends that the wrongly dialled party politely inform the caller of that fact, and also that the caller apologize rather than simply hanging up. Often the two parties will confirm whether or not the intended number is indeed the number that was reached (e.g. "Is this 555-0184?") before ending the call. It is widely considered "dangerous" for the called party to disclose their phone number — rather it is considered more prudent to require the calling party to state which number he dialled and for the called party to simply confirm whether or not that is his number.
See also 
- Lee Lapin, How To Get Anything on Anybody 3, p. 560
- "Dialling mix-up on hospital calls". Newbury Today. 7 April 2007. Retrieved 2 February 2012.
- "Calling Sheffield 0114 3 . . . . . . .". The Star. 18 June 2009. Retrieved 2 February 2012.
- Allan J. Kimmel, Ethical issues in behavioral research: basic and applied perspectives, p. 135