Not long ago, I was called by a woman while I was in the study. She felt she had some demons in her house and asked me to come expel them. Unfortunately, I did not take Exorcism 101 in college! Seriously, she needed an in-depth Bible study; more than what I could do on the phone. I was not in a position to go study with her at that time and would not have, without another female - preferably Rachel - to accompany me.
I did direct her to read her Bible in two places in particular - Matthew 12 and Ephesians 6. Matthew 12 is one account of half a dozen in which Jesus or an apostle cast out an unclean spirit (demon). Demons are evil angels in the service of Satan (Matthew 25:41). God allowed evil spirits to leave the unseen world for a period of time to give Jesus and His apostles an opportunity to show vividly that Jesus has more power than the Devil.
In Matthew 12, Jesus told the Pharisees who accused Him of casting out demons by the power of Satan, "If I cast out demons by the Spirit of God, then the kingdom of God has come upon you." Casting out evil spirits was designed to show three things: 1.) the kingdom of God was about to be established; 2.) Jesus was He Whom He said He was - the Son of God, Savior; 3.) Jesus has more power than the Devil.
That being the case, there is no need to allow demon possession today. The kingdom of God is already established and the Bible proves that. Jesus stands proven to be the Son of God (John 20:30-31) - the Bible proves that. Jesus still has more power than the Devil - the Gospel accounts prove that definitively. So, demon possession would serve no purpose today.
For those - like that lady on the phone - who are afraid of the Devil, Paul wrote Ephesians 6. He writes, beginning in verse 12: "For we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over this present darkness, against the spiritual forces of evil in the heavenly places. Therefore take up the whole armor of God that you may be able to withstand in the evil day, and having done all, to stand firm. ...praying at all times in the Spirit, with all prayer and supplication. To that end keep alert with all perseverance, making supplication for all the saints" (Ephesians 6:12-13, 18).
Of course, in between verses 13 and 18 is the "whole armor of God" (panoply in the Greek). Every item in our armory is related in one way or another to the Word of God.
The bottom line is that Jesus is stronger than the Devil and He can eradicate our fears if we'll submit our lives to Him and follow His Word. That's what I tried to explain to the lady on the phone.