United Medical Doctors

Notes

Country Phone Information

Understanding USA Phone Numbers: Structure, Formatting, and Key Details

Phone numbers in the United States follow the North American Numbering Plan (NANP), a system shared with Canada, parts of the Caribbean, and other U.S. territories. Each U.S. phone number consists of 10 digits, structured under a standardized format for consistency and ease of use.

Basic Structure

• Country Code: The U.S. country code is +1, which must be dialed when calling from abroad.
• Area Code: A 3-digit geographic identifier (e.g., 212 for New York, 310 for Los Angeles). Originally tied to specific regions, area codes now often overlap due to increased demand.
• Local Number: A 7-digit combination, split into:
  • Exchange Code (3 digits): Identifies the telephone exchange.
  • Subscriber Number (4 digits): The unique line identifier.

Common Formats

Domestic:

• (555) 123-4567 (standard)
• 555-123-4567 (alternative)
• 1-555-123-4567 (long-distance)

International:

• +1 555 123 4567 (with spaces)
• +15551234567 (no separators)

Special Number Types

• Toll-Free Numbers: Start with 800, 888, 877, 866, 855, 844, or 833 (e.g., 1-800-HELP-NOW).
• Premium Services: Numbers beginning with 900 charge extra fees.
• Emergency & Short Codes:
  • 911 (nationwide emergency line)
  • 311 (non-emergency services)
  • 511 (traffic/travel info, varies by state)

Dialing Rules

• Local Calls: Most areas require 10-digit dialing, even within the same area code.
• International Calls:
  • To the U.S.: Dial [International Access Code] + 1 + Area Code + Number (e.g., 00 1 212 555 1234 from Europe).
  • From the U.S.: Dial 011 + [Country Code] + [Number].

Mobile vs. Landline

Unlike some countries, U.S. phone numbers do not indicate whether they belong to a mobile or landline. Thanks to number portability, users can keep their numbers when switching carriers or moving.

Scams & Security

Fake caller IDs and spoofed numbers are common in scams. Always verify unknown callers, especially if they claim to be from government agencies or financial institutions.