NPA-NXX - 231-399

This is the 231-399 subcode (NPA-NXX) prefix page. Follow a prefix to find the number you are looking for. We divide our pages up to make them more user friendly to navigate!

1. Area Codes
2. 231
3. 231-399

The 231-399 subcode mainly covers Frankfort in Benzie county. But other numbers maybe included as well.

We have a database of information derived from the public phone records of Michigan state. Many of the numbers in this subcode are Regular Landline registered to Acd Telecom. We hear they employ a large number of people in the Michigan office.
Recently there have been an increase in reported calls, we've had over 17525 comments across our systems for the 231-399 subcode.