How do you know that the right spirit came through & not a bad spirit?
If you have an experienced conjurer/practitioner/practitioner, then you know the difference in energies from long-term exposure & experience. I would know a Vampire from an Angel is a split-second during the conjuration process because their energies are very different. The odds you use a Djinn invocation & a Fae comes through is next to nothing in odds. Invocations, when properly written, conjure only the intended target & nothing else. This is why it's important to work with an experienced & respected practitioner. Otherwise, you leave yourself open to chance. With venues like eBay you don't know who the people are or how experienced or intelligent they are in the practice of spirit conjuration. They could be fresh out of the gate, in which case they shouldn't be working with anything too complicated, and if they did it could cause some real issues. Most people on eBay don't state where they learned how to do what they do, and what their ideology or methodology is.