Using the new 435 area code is mandatory beginning Sunday for long-distance calls to Utah numbers outside the Wasatch Front and Morgan County.
The new area code has been optional since it was first brought into use one year ago. Mandatory use of the 435 area code was to have begun in March, but phone companies persuaded the Public Service Commission to extend the deadline six months.Customers in Weber, Morgan, Davis, Salt Lake and Utah counties will retain the 801 area code. The 435 area code applies to Utah's other 24 counties.
US WEST has been publicizing the approaching deadline in advertisements and in billing statements.