A Christian can be a saved, tongue talking and demon casting but still have a demon oppressing him/her in a form of poor finance, health challenges, death. In view of this Apostle Paul said not to be ignorant. We must understand that we are in a warfare, not with physical powers but with thoughts and any imagination that exhort itself against the knowledge of God.
There are 4 levels of powers we are in battle with as described in the epistles and they are:
Each of this varies in their function but the most important thing is that God as given him a name that is above every other name in heaven, on earth and underneath the earth that at the name of JESUS every knee shall bow and every tongues confess that Jesus is LORD. God in his mercy had given us victory in that name.
As believer we cannot be possessed by demons but we can be oppressed by demons. This is when we have not learnt the strategy of resisting the devil.
James 4:7 “ Submit yourself to the lord, Resist the devil and he will flee from you”
The only way to do this to submit yourself to the lord and resist the devil in faith not in fasting, praying or seed sowing but in FAITH
“Above all, taking the shield of faith, wherewith ye shall be able to quench all the fiery darts of the devil”. That faith should be in the Word of God, on all the promises made to us by God.
2 Corinthians 10:5
“Casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ”
Being full of these promises and being conscious of what the word of God says will enable us to us the word of God in collapsing every altar and strongholds that has been erected by ignorance in our minds.
We must learn to leverage on the authority provided us in Christ Jesus.