[break] a promise

to fail to fulfill a commitment or assurance given to someone

She felt guilty for having to break her promise to attend the event due to a last-minute work obligation.
He promised to help with the project, but he had to break his promise because of a family emergency.
The company faced legal consequences for breaking their promise of data security to their customers.
Breaking a promise can erode trust in a relationship, so it's essential to communicate openly.
She couldn't bear to break her promise to her child, so she made sure to attend the school play.