Bismillah
as salam alykom
Jazakum Allah khairan Faris for your detailed reply.
naseeha, under no circumstances this is allowed. People just get decieved and shaytan decorates it form them, calling it different names and giving them various verifications in order to just go ahead with it. This is serious.
if jin can do anything for us, why dont we just go ahead and seek the assitance of One Who Created the jinn. This will be even better.
Try to instil this logic to those who are doing it. la hawla wala qowata ila billah. u need to approach them kindly and logically. Rather than giving them direct fatwas, just tell them how understanding u r to their position and dire need and problem. Then remind them that if u r that understanding how about the One Who Is Merciful, One Who Is constantly watching over us, He must be even more understanding and Knowing. Teach them rather than wasting time trying to connect to jinn with all the effort need or even the mediator, remind them how easy it is to connect to Allah. It does not need more than taking wodu and standing there starting the meeting whenever u decide not the KIng of the KIngs. Remind them how Allah Is just waiting for us to call upon HIm and Allah Shall immediately respond.
To do this without making a huge mess, u need to approach the person in an indirect manner, like tell him/her that u read on the Internet about how people may resort to jinn for assistance, how harmful this might be. Like usually to do so, people get the assistance of humans who claim ability to connect with jinns. Tell him those people are not but magicians who usually make spells on the one who is seeking help. Thus the person rather than helping him/herself actually harms him/herself. At this point, u can then bring in the betterment of establishing a direct line with Allah, how easy, free of charge and even soothing. Remind the person how u may or someone else have been in a problem and was able to get out thru Allah's and Allah's alone help. Insh aAllah this will work. May Allah Makes your effort a success. Dont forget to take the niyah of helping a Muslim out of shirk.
May Allah Help u to address this problem the best way.
but before doing all this, just make two Raka to Allah (Qadaul haja) and recite Ayahtul korsi before talking to them in order to eliminate the interception of shaytan.
May Allah Assist u much brother ameen