Martin Luther cites Isaiah in the explanation of his shorter catechism, addressing the necessity of praying only to God.

Look down from heaven and see, from your holy and beautiful habitation. Where are your zeal and your might? The stirring of your inner parts and your compassion are held back from me. For you are our Father, though Abraham does not know us, and Israel does not acknowledge us; you, O Lord, are our Father, our Redeemer from of old is your name.  –Isaiah 63:15-16

No where does Scripture commend the idea of praying to the dead or anyone else other than God. The witch of Endor is as surprised as anyone that Samuel actually shows up, and she is hardly an example to follow (1 Sam. 28). But efforts to communicate with lost loved ones are as common as they are tragic. Many of those seeking to contact the dead are searching for consolation and peace, for things to be said and heard, to make up for things done and left undone in the wake of the loss of someone. Instead of healing the wound, such attempts at communication are futile and misleading if not worse. Abraham is the father of the faithful, and from Jesus’ parable about the rich man and Lazarus (Lk. 16:19-31), we know that Abraham’s bosom was the destination of the faithful departed. Who else could hear us if not Abraham? But Isaiah is clear. Neither he nor Israel know what is going on. This is okay because God our Father does know us and our issues. This means that though the pain of loss and separation are real, so is his knowledge and comfort; his grace is sufficient for this trial. It also means that whatever conflicts, issues or sins remain unaddressed between people who are separated by death, they will be resolved if they need to be in the future, and until then there is peace to be had in the here and now.