(1) his power is limited by God’s will (Job 1:10-12; 1 Corinthians 10:13).
(2) as “the god of this world,” Satan has dominion over those who live without Christ in the world (2 Corinthians 4:4).
Don't get me wrong there are those who suffer under direct satanic control... Such as the young medium of Philippi (Acts 16:16-19). And there are those who have devoted themselves to the devil’s work, such as the sorcerers Simon (Acts 8:9-11) However, in each of these examples, the power of God prevails over Satan’s... In fact, Simon is offered a chance to repent (Acts 8:22). Obviously, there had been no irrevocable “selling” of Simon’s soul.