They failed to keep their word.

他们没有信守诺言。

youdao

Consistency: Most people prefer to keep their word.

言行一致：大部分人都想要成为一个说到做到的人。

youdao

What we are worried about is that they won't keep their word.

我们所担心的是他们不能兑现他们的承诺。

youdao

But the pirates did not keep their word.

VOA: special.2009.05.27

People are more likely to keep their word when they verbally agree to something in advance.

FORBES: Persuading People to Keep Appointments

Serving as the honest and fair check on majority power, we will work to ensure they keep their word.

CNN: Commentary: Big risk in Obama's economic stimulus plan

The prime minister warned that if "they do not keep their word, there will be consequences for our relations with Italy".

BBC: Indian warship alongside the Italian cargo vessel