“The 305” is shorthand for the Miami-Dade area, but telephones in Miami-Dade and Monroe counties will soon be assigned numbers with a new area code: 645.
The new code was assigned because the 305 and the counties’ second area code, 786, are running out of possible combinations.
Existing customers will keep their current telephone numbers. New customers, or requests for additional lines, may get he new 645 area code, once it’s activated.
The other two area codes are expected to run out of possibilities by 2023.
More information is available at Consumer Assistance Summary. The 305 number is Florida’s original area code.
– Anne Geggis, Florida Politics