Rowland Heights and City of Industry, California, changed from area code 818 to 626 in 1997. As of 2012, there are no plans for further area code changes in the 626 area.
Since Southern California now has four area code overlays (new area code serves the same geographic territory as the old code, and existing numbers do not change), it is likely that, when 626 begins to run out of telephone numbers, it will add an overlay, rather than undergoing another split.
McHenry, Illinois, has been in area code 815 since the introduction of the original area code system in 1947. On March 17, 2007, area code 779 was added as an overlay on 815.
In 2001, area code 973 in northern New Jersey was overlaid with area code 862. The overlay code was originally announced to be 356, but was changed.
There have been no area codes in England, or the rest of the United Kingdom, that begin with '04' since the year 2000. If the number you have dates from before the major national renumbering in year 1995, it would be the code for Guildford. That code has since changed to 01483.
No, area code 856 covers the exact same part of southern New Jersey that it did when it was created in 1999.
If you mean that you have a phone service which has the wrong area code in its number, you need to contact your phone service provider to get it changed.
San Antonio, Texas, was in area code 512 from 1947 (when area codes were first introduced in the US and Canada) until November 1, 1992, when it changed to area code 210. In 1992, not only San Antonio, but also the Hill Country (now area code 830) and the Rio Grande Valley (now area code 956) changed from 512 to 210. In 1997, 210 underwent a three-way split, creating the current 830 and 956 area codes.
Area code 343 has been assigned in Canada, to overlay the 613 area code in Eastern Ontario. This area includes Ottawa
St. Charles, Illinois, changed from area code 708 to 630 in 1996.St. Charles was in area code 312 until the 312/708 split in 1989.
North American area code 840 has not been assigned.
From 1947 until 2001, Rochester and Buffalo, New York, shared area code 716. Permissive from 2001-11-15, and mandatory from 2002-08-17, Rochester and the eastern portion of 716 changed to 585.
In an area code split, or another situation in which all the numbers in a portion of a geographic territory are changed, the area code is changed automatically in the telephone switches and in mobile handsets. Other than that special case, it is not generally possible to change only the area code while retaining the same local number (for example, to change your number from 213-555-0123 to 619-555-0123).
Area code 972 was created in September 1996. However, no numbers changed from 817 (Fort Worth) to 972 (Dallas).