As of yesterday, Brooklyn has a fourth area code--929-- giving Brooklyn, the Bronx, Queens, and Staten Island a total of four: 718, 347, 917, and 929. Equipment that currently has a 718 or 347 area code is keeping that code. Most Brooklyn land line phones have a 718 code, but newer lines, including cell phones, have been getting a 347 or 917 area code assigned to them.
Verizon says
"Bronx, Brooklyn, Queens, and Staten Island customers requesting new service, an additional line, or in some cases, moving their service may be assigned a number in the new 929 area code. The 929 area code will co-exist everywhere in Bronx, Brooklyn, Queens and Staten Island with the 718, 347 and 917 area codes."
Verizon promises that "The price of a call, coverage area, or other rates and services will not change."
The Federal Communications Commission says that if you move within your geographic area, local number portability (LNP) allows you to switch telephone service providers--including switching from a wireless, land line, or interconnected Voice over Internet Protocol (VoIP) provider--and keep your existing phone number.
However, if you move outside your geographic area, your number may not be portable.