"Go back on" is a phrase that is frequently used to indicate breaking a promise or going against one's word. You can use synonyms like retract, recant, backtrack, or renege to express a situation where someone has gone back on their words. Another phrase that can be used as a synonym for "go back on" is "reverse course." This phrase means they have done an about-face from what they had previously promised. Some other synonyms which can be used for this phrase include betray, disappoint, fail, deceive, and breach trust. It is important to know various synonyms for a single word to elevate your writing skills and make your content more diverse.