What is so disheartening is that you can show some of these people Scripture and it doesn't matter because "God spoke to them" and told them what to believe. I often tell these people that claim to hear the voice of the Creator that I've heard other people claim the same but tell me that God spoke to them something quite different.
For instance I know of two ministers who claim that God told them individually what His name is. One minister told me that God said His name is Jesus; the other minister told me that God said His name is the Lord God. Which one is right? Well, if you go by what people are telling you there is no way of knowing. However, if you judge what they claim by Scripture you can know the truth.
Scripture ALWAYS trumps what people claim to hear from heaven. The Apostle Paul even said that if an angel from heaven came teaching another gospel let him be accursed (Galatians 1:9). The people of Berea were praised for checking Paul's doctrine out by examining the Scriptures daily (OT Scriptures) to see if what he was telling them was the truth (Acts 17:10-11).
There was a time when God's revelation was orally transmitted; that time has come and gone. Once His revelation was written down it cannot be improved upon, added to, or taken away from. Do not listen to people that claim God spoke to them; be very cautious. Instead go with what Scripture says. That is how you will hear Yahweh speaking to you today.
EMJ