In December of 2014 the North American Numbering Plan Administrator (NANPA) officially implemented a plan to deploy a new area code in Suffolk County. The Administrator put in motion a shift that would allow for two different area codes to service the same area–Suffolk's existing 631 area code and the new 934 area code.
Now, nearly 18 months later, Long Island is fast approaching the launch of the new area code. Under NANPA's plan no existing phone lines in Suffolk will need to switch their area codes, but as of July 16, 2016, new lines and services will have the potential to be issued a number under the new 934 code. Both area codes will operate within all of Suffolk, but the overlay should not affect billing or charges for calls within the county.
Perhaps the most inconvenient aspect of the new area code is that Suffolk residents will now need to dial the full phone number–area code included–for all calls. Beginning June 18th, almost a full month before 934 numbers are first issued, even calls placed from one 631 number to another (or, later, one 934 number to another) will require that the full 10-digit number is dialed. Failure to include the area code will result in a recording instructing callers to hang up and dial again.
The requirement for area codes will, of course, affect cellphone phone books and speed dial functions as well, meaning that anyone who has stored a phone numbers onto their phones will need to make sure that the appropriate area code is also saved in order for call placed from their devices to connect.
[Source: NYS DPS]