I must distinguish between human smuggling and human trafficking. Human smuggling involves an arrangement where someone pays for passage. Human trafficking is where people are coerced and forced for either sexual or labour exploitation.
In some cases it can transition from human smuggling to human trafficking, when individuals who are smuggled are indebted to criminal organizations and still owe a debt. Sometimes that involves being exploited in order to pay off that debt, or being employed in a criminal enterprise to work down the debt.