It would be nice if you could indicate which Bible passages you're referring to.
Paul does refer to a natural man and spiritual man when he writes to the Corinthians. Now these Corinthians are already saved, redeemed, regenerate, and indwelt saints. Why would Paul talk to regenerated saints about a "natural man"? That's because that Church was well known for its congregation that was still “carnal” (1 Cor 3:3) and was still “babes in Christ” (1 Cor 3:1). Paul was admonishing all church members to embrace that which the Holy Spirit teaches and not to be a “natural man” who knows nothing of the things of the Spirit. Paul was not talking exclusively about unregenerate man. It would be out of context to use those verses in that way. Paul was talking to the entire Corinthian congregation that they need to be a spiritual man and not a natural man. Paul's message is to the entire congregation to stop being carnal and to grow up spiritually. That is a message for all regenerates.
You may want to read the actual passage I Corinthians 2 "
9 But as it is written, Eye hath not seen, nor ear heard, neither have entered into the heart of man, the things which God hath prepared for them that love him.
10 But God hath revealed them unto us by his Spirit: for the Spirit searcheth all things, yea, the deep things of God.
11 For what man knoweth the things of a man, save the spirit of man which is in him? even so the things of God knoweth no man, but the Spirit of God.
12 Now we have received, not the spirit of the world, but the spirit which is of God; that we might know the things that are freely given to us of God.
13 Which things also we speak, not in the words which man's wisdom teacheth, but which the Holy Ghost teacheth; comparing spiritual things with spiritual.
14 But the natural man receiveth not the things of the Spirit of God: for they are foolishness unto him: neither can he know them, because they are spiritually discerned."
This has nothing to do with carnality in the church. Paul is speaking of people who are not saved. This is not Paul's audience, for what does Paul say of his audience? "12 Now we have received, not the spirit of the world, but the spirit which is of God; that we might know the things that are freely given to us of God." and into verse 13.
Our salvific belief comes about as a reaction to the effectual Word of God for those who believe, not that the elect are regenerated to believe.
Saul's Damascus story doesn't show that at all. In fact, it shows Saul regenerated into Paul, before Ananias ever gets the chance to teach him more about Jesus and God. What came to Ananias was the self-reflective, introspective Paul. Who left Ananias was the saved Paul. I think there is a reason why God made a whole show of the scales falling from Paul's eyes after he meets Ananias.
1 Th 2:13 And for this cause we thank God without ceasing, that when you received the Word of hearing, of God, you welcomed it as the Word of God, not as a word of men, but as it is, truly the Word of God, which also effectually works in you who believe.
Read also Rom 10:8-18 for more details on the effectual Word of God.