For your position to work, that those saved cannot fall, you have to use the words of the Bible in a very awkward way that contradicts how the word is defined. That doesn’t make sense.
For example, take the use of “remain”. Look up this definition of remain:
thefreedictionary.com/remain. It means to stay in the same state or place.
A person cannot “remain” where he or she has not been.
This is not a bit theological term, like justification. It is simple, common, and straightforward.
Here are some pertinent uses in the New Testament:
Whoever eats my flesh and drinks my blood remains in me, and I in him. (John 6:56).
Remain in me, and I will remain in you. No branch can bear fruit by itself; it must remain in the vine. Neither can you bear fruit unless you remain in me. (John 15:4)
"I am the vine; you are the branches. If a man remains in me and I in him, he will bear much fruit; apart from me you can do nothing. (John 15:5)
If anyone does not remain in me, he is like a branch that is thrown away and withers; such branches are picked up, thrown into the fire and burned. (John 15:6)
– Jesus doesn’t say those not remaining with him were not branches at all, He says they were branches, and will now be cast into the fire because they did not remain (or stay in the state of faith in Him).
If you obey my commands, you will remain in my love, just as I have obeyed my Father’s commands and remain in his love. (John 15:10)
When he arrived and saw the evidence of the grace of God, he was glad and encouraged them all to remain true to the Lord with all their hearts. (Acts 11:23)
– in this last passage, “remain true to the Lord with all their hearts” strengthens the concept remaining or being in the body of Christ, as it shows that “remaining true” is an expression of showing total fidelity with faith in Jesus.
… strengthening the disciples and encouraging them to remain true to the faith. (Acts 14:22)
True to the faith? That can’t be other than remaining faithful to something they believed in.
But Paul and Barnabas remained in Antioch (acts 15:35)
I included this one to show how remain is used. It definitely meant to stay in a place, even back then. The word meaning has not changed.
Here is a link with all the other times “remain” is used in the New Testament. It always means that someone was in a place or state already.
biblegateway.com/keyword/?search=remain&version1=31&searchtype=all&spanbegin=47&spanend=73
Here is another phrase used to show that someone had belief in Christ, and now can fall:
"For if we sin deliberately after receiving the knowledge of the truth, there no longer remains a sacrifice for sins, but a fearful prospect of judgement,
It says there is “no longer remains” etc. This meant there used to be a state where there was a sacrifice for sins. That can only happen for that person if they were saved (in your words), or believed.
The concept of OSAS only holds when the words of Scripture are taken out of normal meaning and bent to the dogma, and not the other way around, that the dogma should be realized from the words of Scripture (which is the way it should be done). Protestant theology came as a “reaction” to what Martin Luther and others saw first as abuses of the Church. It was not developed during a time of exploring God’s grace.
All the pieces of it have to lock together for any of it to hold. This means that, when faced with contradictory evidence from Scripture, the meaning of those passages has to be changed to fit. This is not good. Further proof of this is that each Protestant group twists it a bit differently. For example, some say you cannot fall, others that those who fall were never believers. This lack of consistency arising from the same time period and belief show a weakness there.