Does God Change His Mind?

What had Paul warned before they left Fair Havens?
"Men, I perceive that this voyage will end with disaster and much loss, not only of the cargo and ship, but also our lives" (Acts 27:10).

Since their lives will be spared, had Paul's perception in Fair Havens been wrong?
It's more likely that Paul, along with Luke and Aristarchus, had been praying throughout Euroclydon for God to spare the lives of those onboard, and in response to those prayers, God had changed His mind and told the angel to tell Paul, "God has granted you all those who sail with you" (Acts 27:24).

Then why did God say, "For I am the LORD, I do not change" (Malachi 3:6)?
God's nature doesn't change, just as He declared above, for God is always loving, merciful, compassionate, gracious, holy, and just. What does change are God's plans in response to our rebellion, obedience, and prayers. For example, if we sin, God relents on His planned blessings, for God is just; but if we repent of our sins, God relents on His planned punishment, for He is also merciful: "The instant I speak concerning a nation and concerning a kingdom, to pluck up, to pull down, and to destroy it, if that nation against whom I have spoken turns from its evil, I will relent of the disaster that I thought to bring upon it. And the instant I speak concerning a nation and concerning a kingdom, to build and to plant it, if it does evil in My sight so that it does not obey My voice, then I will relent concerning the good with which I said I would benefit it" (Jeremiah 18:7-10). And God, who is also compassionate, changes His mind in response to our prayers, as He appears to have done with Paul's above, and with Hezekiah's: In those days Hezekiah was sick and near death. And Isaiah the prophet, the son of Amoz, went to him and said to him, “Thus says the LORD: ‘Set your house in order, for you shall die and not live.’ ” Then Hezekiah turned his face toward the wall, and prayed to the LORD, and said, “Remember now, O LORD, I pray, how I have walked before You in truth and with a loyal heart, and have done what is good in Your sight.” And Hezekiah wept bitterly. And the word of the LORD came to Isaiah, saying, “Go and tell Hezekiah, ‘Thus says the LORD, the God of David your father: "I have heard your prayer, I have seen your tears; surely I will add to your days fifteen years" (Isaiah 38:1-5).