I was recently asked by the cluster chair to organize a session at a conference on topic X. How does one go about organizing a conference session?
In my field, applied mathematics, this would mean find 4-8 people who are willing to participate in the conference and give a talk in your session. Small print: they are going to have to pay their own conference fee, and we do not reimburse any expense to them or give financial support of any kind.
Typically you find these people by asking them in person or sending them an e-mail. Do not overbook, as people accept more often than not, if it is a good conference.
This is how most conference sessions are organized -- if the conference itself is respectable, there is nothing suspicious about it.