Here’s a quick example from my AM bible reading of God changing his plan in response to prayer.
See 1 Kings 20:1-6.
Prophet Isaiah announces for the LORD that Hezekiah will die and needs to put his “house in order.”
Hezekiah prays and weeps before the LORD.
While Isaiah is leaving Hezekiah, God instructs him to go back to tell Hezekiah he’s heard his prayer and is granting him fifteen more years of life.