Did God change His Mind is what I asked you.
You tell me. God told Hezekiah that he was going to do. After Hezekiah prayed, God allowed him to live another 15 years. God changed his mind about Hezekiah dying. God did not lie.
David knew this about God as well. The man after God's own heart.
2 Samuel 12
14 Howbeit, because by this deed thou hast given great occasion to the enemies of the Lord to blaspheme,
the child also that is born unto thee shall surely die.
15 And Nathan departed unto his house. And the Lord struck the child that Uriah's wife bare unto David, and it was very sick.
16
David therefore besought God for the child; and David fasted, and went in, and lay all night upon the earth.
17 And the elders of his house arose, and went to him, to raise him up from the earth: but he would not, neither did he eat bread with them.
18 And it came to pass on the seventh day, that the child died. And the servants of David feared to tell him that the child was dead: for they said, Behold, while the child was yet alive, we spake unto him, and he would not hearken unto our voice: how will he then vex himself, if we tell him that the child is dead?
19 But when David saw that his servants whispered, David perceived that the child was dead: therefore David said unto his servants, Is the child dead? And they said, He is dead.
20 Then David arose from the earth, and washed, and anointed himself, and changed his apparel, and came into the house of the Lord, and worshipped: then he came to his own house; and when he required, they set bread before him, and he did eat.
21 Then said his servants unto him, What thing is this that thou hast done? thou didst fast and weep for the child, while it was alive; but when the child was dead, thou didst rise and eat bread.
22 And he said,
While the child was yet alive, I fasted and wept: for I said, Who can tell whether God will be gracious to me, that the child may live?