I believe Peter was a Christian...
Acts 2:38... Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for ther emission of sins, and ye shall receive the gift of the Holy Ghost.
Do you?
The problem you have is that Philip went to Samaria, he preached and baptized in the name of Jesus. All believed, but none received the gift of the Holy Spirit. Peter and John had to come and lay hands on them before they received the gift.
So either Peter was wrong in Acts 2:38, or you should refrain from chucking a good hermaneutic out the door.
2
And he said to them, Did you receive the Holy Spirit when you believed? And they said, No, we have not even heard that there is a Holy Spirit. 3 And he said, Into what then were you baptized? They said, Into John's baptism. 4 And Paul said, John baptized with the baptism of repentance, telling the people to believe in the one who was to come after him, that is, Jesus. 5 On hearing this, they were baptized in the name of the Lord Jesus. 6
And when Paul had laid his hands on them, the Holy Spirit came on them, and they began speaking in tongues and prophesying. 7 There were about twelve men in all.
12 But when they believed Philip as he preached good news about the kingdom of God and the name of Jesus Christ, they were baptized, both men and women.
Peter and John, 15 who came down and prayed for them that they might receive the Holy Spirit, 16 for he had not yet fallen on any of them, but they
had only been baptized in the name of the Lord Jesus.
17 Then they laid their hands on them and they received the Holy Spirit.