Simplicity does not mean believing whatever anyone tells you and foolishly falling victim to dishonesty and falsehood. That would be gullibility, not simplicity.
Our Sages warned us in this regard: Respect, yet suspect that which is unfamiliar to you (cf. Derekh Eretz Zuta 5).
Rebbe Nachman specifically warned us to be very careful in financial matters (see Likutei Moharan I: 69; cf. Sichot HaRan #281) and to be wary of placing our physical well-being and/or emotional welfare in the hands of “reliable” professionals and “tried and tested” solutions (Sichot HaRan #50).
From Rebbe Nachman and YOU, by Chaim Kramer