Individuals seeking admission to the United States in a nonimmigrant category must be inspected in person by an immigration officer at an official U.S. port of entry (POE). Before inspection, most arriving aliens are seen as "applicants for admission." Individuals also go through customs inspection at most ports of entry.

The U.S. Customs and Border Protection (CBP) Office of Field Operations (OFO) is responsible for determining the admissibility of travelers at U.S. ports of entry.

It is important that you check your most recent I-94 record every time you enter the US. 

The I-94 is the record of arrival and departure issued to visiting or transiting persons to the United States except U.S. citizens, returning foreign visitors, foreign visitors with immigrant visas, and most Canadian citizens. Your I-94 must show the immigration status that you entered the US with, and "D/S" which means that you've been entered for the duration of status on your  DS-2019.

Non-U.S. citizens traveling to the United States  may also download the free CBP One mobile app from the Apple App Store or Google Play and complete an electronic I-94 form up to seven days before their trip. The feature provides a more convenient way for travelers to apply for an I-94, review their past travel history, check their I-94 expiration date and obtain proof of their electronic I-94 from their mobile device.

Sometimes the officer reviewing your case will make a mistake. It is your responsibility to check your I-94 for errors and have them corrected. If you spot a mistake, please contact the Deferred Inspections Office at the airport you first entered into the US through. Usually the error can be corrected over the phone or by email, but sometimes you may need to visit the office at the airport.

Philadelphia Deferred Inspections Office:

Address: Terminal A West 3^rd Floor International Arrivals Hall - Philadelphia International Airport
Phone: (215) 863-4247
Email: philadeferredinspections@cbp.dhs.gov