1
                           general:: 
                            Phrase(s): go back on one’s word [and] go back on one’s promise; go back on one’s pledge 
to break a promise that one has made.  •  I hate to go back on my word, but I won’t pay you $100 after all.  •  Going back on your promise makes you a liar.
                        
                        
 
                        
                            McGrawhill's American Idioms And Phrasal Verbs