We are not to contact the departed or attempt to communicate with them. If you think otherwise show where the apostles taught it.
Exactly which departed Christians would they have been communicating with? And given that they were still receiving devine guidance, perhaps redundant.
I take the point however, and in fact, do not seek the prayers of passed souls myself. But then I don't ask for prayers at all as a general rule. Bad on me.
Conjurring up the dead should not be attempted; however, speaking in the hope that they hear you is not the same thing. The differentiation is something that Catholics should probably spend more time discussing.