I am curious, would contact with the dead be a sin if it was not used to divine the future or influence future events? Just for say, a good chat?
No.
... or influence future events?
Depends on what you mean by "influence." Since much prayer is petitionary, and since intercessory prayer means asking somebody else to make a petition to Almighty God, we can justifiably hope to "influence" future events by means of such prayer. Just as if you were to ask your mom, "Please pray that my wife's surgery turns out OK."
Just for say, a good chat?
(Smile) I don't know whether "chat" quite describes it, since I, for instance, have never heard anything like a repartee!