This is not the area my paper covers, and I don't want speak about any particular NGO by name, but creating a hyperbolic tale of "sex slaves" makes money for NGO's. In reality, if it's in fact the nightmarish horror that image conjures, I'm pleased to let you know law enforcement, government and charity is abundant for these victims.
Victims are helped, perpetrators are punished. For example, in China, pimping can have you executed. Every country offers counselor services where they'll print them a new temporary visa and even a ticket back home.
Many choose not to, they'd rather go try to find a way to go through the immigration system and get citizenship. This is off topic of my paper, but being a female and having a child may earn the mother favor toward getting naturalized in many places (laws, department/ministry policies or judge discretion).
Regarding the different NGO actors, this is even farther away from my area. But sometimes NGO's are actually fronts for GO's. An example would be USA using NGO's for subversion in Russia (https://en.wikipedia.org/wiki/Russian_foreign_agent_law#Impl...). That said, way out of the area I'm collecting data on.
Regardless, this thesis is only a thesis. "Exposing" those who misrepresent NGO's isn't a career. What I want to tell you is that a lot of people pass on a humanistic message, when they're really hustling people.
If you do care about people, I think the best thing you can do is volunteer your time, skill and expertise. A good example is Médecins Sans Frontières.