Sorry, you are wrong brother. Pray about it. I got the information (and held it up to the Word) from Hank Hanegraaff aka "Bible Answer Man". He is one of the most well respected teachers of modern times and a very wise Christian believer.
I believe Scripture I quoted speaks enough. Jesus Christ made it clear that evil and Holy Spirit cannot dwell in the same room. Therefore, the devil (possessed) cannot dwell in a Christian (filled with the Holy Spirit).
You have not provided Scripture to back up your statement. That is part of the forum rules to do so to avoid misunderstandings. Please show me any example in Scripture where a Holy Spirit filled Christian was possessed.
John 14:16-18
16 And I will pray the Father, and He will give you another Helper, that He may abide with you forever— 17 the Spirit of truth, whom the world cannot receive, because it neither sees Him nor knows Him; but you know Him, for He dwells with you and will be in you. 18 I will not leave you orphans; I will come to you.
A person who has slipped so far away from GOD has possibly rejected the Holy Spirit, making him or her prone to being demon possessed if not oppressed.
Here is a great article from Gotquestions.org all quoting Scripture as well:
Question: "Can a Christian be demon possessed?"
Answer: The Bible does not explicitly state whether a Christian can be possessed by a demon. However, since a Christian is indwelt by the Holy Spirit (Romans 8:9-11; 1 Corinthians 3:16; 6:19), it would seem unlikely that the Holy Spirit would allow a demon to possess the same person He is indwelling. We definitely recognize that this is a controversial issue.
However, we strongly hold to the belief that a Christian cannot be possessed by a demon. We believe there is a sharp difference between being possessed by a demon, and being oppressed / influenced by a demon. Demon possession involves a demon having direct control over the thoughts and/or actions of a person (Luke 4:33-35; 8:27-33; Matthew 17:14-18).
Demon oppression / influence involves a demon or demons attacking a person spiritually and/or encouraging him/her into sinful behavior (1 Peter 5:8-9; James 4:7). You will notice that in all the New Testament passages dealing with spiritual warfare, we are never told to cast a demon out of a believer (Ephesians 6:10-18). We are told to resist the devil (1 Peter 5:8-9; James 4:7), not to cast him out.
It is unthinkable to me that God would allow one of His children, whom He purchased with the blood of Christ (1 Peter 1:18-19) and made into a new creation (2 Corinthians 5:17) – to be possessed and controlled by a demon. Yes, as believers, we wage warfare with Satan and his demons, but not from within ourselves. 1 John 4:4 declares, “You, dear children, are from God and have overcome them, because the One who is in you is greater than the one who is in the world.” Who is the One in us? The Holy Spirit. Who is the one in the world? Satan and his demons.