Oneness Pentecostalism theology takes some truth from the Bible and convolutes it. Their theology denies the doctrine of the Trinity. As much as the Oneness Pentecostalism cult properly discerns that there is only one God they are confused about who He is and incorrectly teach and believe that God is a single person when the true biblical doctrine of the Trinity teaches there is one God–who exists in three separate persons; yet still one God. Oneness doctrine teaches that the one person in the Godhead is named Jesus and that Jesus is also the Father and the Holy Spirit. This is not what the Bible teaches.
We need only to refer to when Jesus was in the Garden of Gethsemane when Jesus prayed to the Father, making the distinction that the Father’s will and Jesus’ will are two separate wills, one of the Son and one of the Father.
Oneness theology also relegates baptism into a strict “must do” which must be adhered to in order to achieve salvation. They essentially discard the doctrine of grace and add on works and rituals as most cults do. This group teaches that the baptism by immersion must be executed exclusively by a: Oneness Pentecostal minister to be valid and it must be done in the name of “Jesus” and not “In the name of the Father, the Son and the Holy Spirit.” They also teach that it is possible to lose one’s salvation.
Oneness Pentecostals teach that without speaking in tongues that the Holy Spirit is not present and since the Holy Spirit must be present in order to be saved, then according to the Oneness Pentecostals those who do not speak in tongues are not saved. The Oneness groups encourage speaking in tongues to show “evidence” that they are saved. Tongues as referred to in the book of Acts was done to translate literal languages so others could understand what was being said when someone spoke in tongues, i.e., known human languages, not gibberish as in what some call a “prayer language” or “heavenly language.” In fact Paul placed the gift of interpretation of tongues more highly as it would edify the entire church (1 Corinthians 14:4-5).
The Oneness Pentecostal adherents are varied and have many followers. The two most well known that fall under the Oneness Pentecostal umbrella are the United Pentecostal Church International, the United Apostolic church, theAssemblies of the Lord Jesus Christ, the Bible Way Churches of Our Lord Jesus Christ and countless others dispersed throughout the United States.
On a positive point, The Oness people try to maintain a holy and discreet lifestyle but legalistic tendencies to judge a person by certain standards override their good intntions. For example, there are strict dress codes for acceptance into a Oneness Pentecostal church. And if you a ttend any movies or watch television you might be considered not “really Christian.” There seems to be no happy medium, only extreme aberations of the Scriptures.
Following is a list of some of the problematic beleifs that the Oneness Pentecostals teach: 
1. Denies the doctrine of the Trinity.
2. Denies justification by faith alone by stating that baptism is also required for salvation.
3. Jesus is God the Father.
4. Jesus is the Holy Spirit.
5. Denies pre-existence of the Word as the Son. Teaches that the He existed as the Father.
6. Being born again means repentance, baptism, and speaking in tongues.
7. Speaking in tongues is a necessary requirement to demonstrate that a person has been baptized in the Holy Spirit, and is, therefore, saved. It is claimed to be the initial sign of the infilling of the Holy Ghost.
8. Women may be pastors.
9. Only Oneness adherinsts will go to heaven
What makes this and many other cults especially confusing is that some of their teachings are inline with the Scriptures and initially their off-the wall teachings may be camoflauged because some of the valid teachings of the Bible are mixed in with their altered versions.