The Body of Christ was predetermined... corporately. Not individually.
If people were either predetermined to go to heaven or go to hell prior to their birth there would be no point in the gospel, no point in God's word at all. Those that would be saved... would be saved. Those that are destined to hell would be destined to hell. No sense in preaching the gospel or being compelled to follow God based on His deeds, word, and love.
The Bible paints a much different picture. A picture about men having the ability to choose to be with Him or not.
Matthew 23:37 “O Jerusalem, Jerusalem, the one who kills the prophets and stones those who are sent to her! How often I wanted to gather your children together, as a hen gathers her chicks under her wings, but you were not willing!
Revelation 22:17 And the Spirit and the bride say, “Come!” And let him who hears say, “Come!” And let him who thirsts come. Whoever desires, let him take the water of life freely.
John 3:16 “For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life.
John 5:40 “But you are not willing to come to Me that you may have life.
2Peter 3:9 The Lord is not slack concerning His promise, as some count slackness, but is longsuffering toward us, not willing that any should perish but that all should come to repentance.