Prefix Information
The prefix 399 is part of area code 406 serving Billings, Montana.
This exchange contains 10,000 possible phone numbers (406-399-0000 through 406-399-9999).
Phone numbers with prefix 399 in area code 406. Location: Billings, Montana.
The prefix 399 is part of area code 406 serving Billings, Montana.
This exchange contains 10,000 possible phone numbers (406-399-0000 through 406-399-9999).