All the texts used by the chat widget (seen by the customer) can be translated or modified to your needs. To do this, go to the Settings → Chat → Translate and Customize

On that page, you can provide customized texts to be displayed to the customer. You can provide a default texts, to be used for all customers, and also localized (translated) versions of the texts, which will be displayed to customers based on their browser locale setting.

You can translate of modify the text by clicking on it (use the search box to find the text that you need):

After changing the text, click the Change button to save the change. You can also reset the text to default by clicking Reset.

Note that texts with parameters require that parameter placeholders, such as {}{0}{1}{2}{3} and so on, are retained in the modified version - this is actually validated and in case of a missing parameter an error is displayed: