In chastising his congregants for consulting astrologers, John Calvin referred to Isaiah 44:25: "[The Lord] frustrates the signs of liars and makes fools of diviners, who turns wise men back and makes their knowledge foolish." The prophet here tells the Israelites that consulting astrologers is dangerous, because God deliberately deceives the deceivers, as punishment for the deceived.
The Prophet Jeremiah also addressed the question of astrologers (Jeremiah 10:2): "Do not act like the other nations, who try to read their future in the
stars. Do not be afraid of their predictions, even though other nations
are terrified by them."
In their advertisements and signs, astrologers, palm-readers, and "spiritual advisors" often include a cross, claiming that their foundation is Christian. It is OK to consult them, we are to believe, because they aren't like Pagan fortune tellers. But God says otherwise.
The person who goes to a fortune teller, whether of the Pagan or the professedly-Christian variety, is looking for a secret source of information, apart from the revelation that God has given us. That in itself is a pagan act, regardless of what Christian terminology anyone uses to clothe it.
Isaiah also addresses that mentality directly (Isaiah 8:19-20): "When they say to you, 'Inquire of the mediums
and the necromancers who chirp and mutter,' should not a people inquire
of their God? Should they inquire of the dead on behalf of the living? To the teaching and to the testimony! If they will not speak according to this word, it is because they have no dawn." "The teaching and the testimony" are biblical words for the Scriptures (see Psalm 119). Thus, God opposes the use of fortune tellers, and directs His people to find their infallible revelation in His word alone. If a person is seeking spiritual knowledge outside Scripture, then he is committing two sins: one is to demonstrate a pagan mentality that seeks truth outside that given by God; and the second is to accuse God of inadequacy. What He gives you, you decide, is not good enough. Do you not recognize that as the same temptation with which Satan destroyed the bliss of our first parents (Genesis 3:1-5)?
No matter what you call yourself, if you consult astrology, or any other type of fortune teller, then you are a Pagan, not a Christian.