Living in Detroit and the southeastern Michigan area, you quickly realize that the local phone number system is divided into several parts.

In the U.S., phone numbers consist of an area code + a 7-digit number, and there are four main area codes used in the Detroit metropolitan area. First, 313 is the area code for the city of Detroit itself, and it is also a symbolic number for the Motor City. The number 313 has become part of Detroit's cultural identity, frequently appearing in hip-hop music and street art.

As you move into the suburban areas, different area codes apply. 248 corresponds to Oakland County and some northern suburban areas of Wayne County, including Bloomfield Hills, Troy, Birmingham, and Pontiac. The Troy and Novi areas, which have a significant Korean community, also use the 248 code. 586 is used in Macomb County, which includes Sterling Heights, Warren, and St. Clair Shores. 734 applies to the suburban areas of Wayne County, particularly the southwestern areas like Ann Arbor, Ypsilanti, and Dearborn.

In the U.S., it is common to need to dial the full 10-digit number even within the same area code, so it is advisable to get into the habit of saving complete numbers that include the area code. If you need a Detroit city number (313) for business purposes, it is possible to obtain a 313 number through Google Voice or VoIP services. The major mobile carriers available in the Detroit metro area are Verizon, AT&T, and T-Mobile, with MVNO services like Cricket, Metro by T-Mobile, and Boost Mobile also operating competitively. You can purchase prepaid MVNO SIM cards at electronics stores like Best Buy or Walmart, which are familiar to many Koreans.

For internet service, Comcast (Xfinity) and AT&T Fiber are the two main providers in the Detroit metro area. Recently, some areas of downtown Detroit have also seen the introduction of Starlink satellite internet operated by Elon Musk's SpaceX, and there has been support for affordable internet connections through the federal assistance program (Affordable Connectivity Program, ACP) for low-income households (current program status needs to be checked). For business operators, clearly understanding the area codes and service areas can help with customer interactions. For example, a 313 number indicates a downtown Detroit customer, 248 indicates an Oakland County customer, and 734 indicates a customer from the Ann Arbor area.

When making international calls to Korea (+82), you can dial 011-82-area code-number from the U.S. or use +82. The time difference between Detroit and Korea is 14 hours during standard time (Eastern Standard Time, EST, UTC-5) and 13 hours during daylight saving time (Eastern Daylight Time, EDT, UTC-4). It is courteous to consider the time difference when contacting family in Korea. Internet-based messengers like WhatsApp and KakaoTalk allow for voice and video calls without international call charges, making them widely used in the Korean community.