I went through a funny situation. I posted an ad for an example dissertation service. A few writers contacted me. One of them sent a resume which looked professional. The resume had all the bells and whistles, including description about the expertise in my subject area.

He offered to write a 2-page literature review as a trial to test him. I agreed and paid half of his normal per-page fee.

One or two days later, I contacted a couple of professional writing services by filling out a contact form on their websites. I thought it would be the safest option in case the freelance writer fails to deliver the trial on time. One of the companies contacted me with a strange message. They basically asked if it was me who ordered a 2-page paper on exactly the same topic (and same instructions) because they are still working on it. They wanted to make sure I don't order twice by mistake. When I replied that I've never ordered from them before and asked for more details, they gave me a small hint which allowed me to realize it was the same person/freelancer who was supposedly working on my trial pages who ordered the paper from them! Then I looked up this person's email and other details online which discuss some Kenyan/African writers with strange-sounding names.

So my conclusion (hopefully it's reasonable enough) is that a writer from Africa has ordered trial pages from a professional service in order to make me believe he would be able to complete the rest of the work for the full amount. Not sure if it makes sense or is even likely, but that's my experience so far. Hopefully some student will find it interesting and useful.