WASHINGTON - Sanjay came to the United States from India on a H-2A visa which allows a foreign national entry into the country for temporary or seasonal agricultural work.

The idea was to make money to send home to his family.

He signed a contract for a job that was supposed to be on a farm harvesting crops. Instead he, and others, were forced to work in construction around hazardous chemicals.

They were not given proper safety gear, and were forced to work 80 hours per week, double the usual 40 hour limit.

Sanjay and others were verbally abused and threatened with arrest, jail and deportation if they did not comply.

Jaclyn was 15 and pregnant when she started texting Gabriel, who offered her a temporary job as an escort in a big city, promising she would make thousands of dollars.

The girl from the north-western US was hesitant. But he promised the work would be just dating, with no sex involved.

Jaclyn took the chance. Gabriel wired her the cash for a plane ticket.

Once she arrived, Gabriel picked her up and took her to a hotel room where he forced her to have sex with him. Then he set her up on her first date.

Jaclyn made it clear to the client that she did not want to have sex. He paid her and left.

When Gabriel returned that evening, he took all her money and told her to go home if she wasn't going to do commercial sex - and abandoned her in the hotel. The teenager was alone, homeless, and penniless in a strange city far from home.

Sanjay and Jaclyn both called the National Human Trafficking Hotline, which provided their stories to The Sunday Times, with names changed and some details withheld.

The hotline has been in existence since 2007, and in that time it has logged 40,200 cases of human trafficking.

The "advocates" who answer the calls speak principally English and Spanish. Translators for other languages are a call away. Law enforcement, health and other services are also a call away.

Jaclyn's case was referred to local police, who found her and helped her get home. Sanjay was given contact information for free legal resources, and referrals to other agencies that assist with safety and working hours issues in the workplace.

Escort services - the kind Jaclyn was lured into - top the list of 25 types of human trafficking the hotline has been able to classify based on its data.

The second most common is trafficking for labour - the kind Sanjay was trapped in.

When they called, there was little doubt that their cases fit three key characteristics that define human trafficking: force, fraud and coercion.

The hotline's advocates sit in a long room along the side of the seventh floor of a building in Washington DC, quietly talking into their phones.

Calls are not recorded; the advocates take notes, spending an average of 15 minutes per call.

Fifteen advocates work during the day and four overnight. Each has two big computer screens.

A bigger monitor on the wall displays calls in progress and those waiting.

By 10.30am on a recent weekday, 49 calls had come in from around the country.