The HelloShift app doesn't have a setting for this, as it is not an easy task to include. However, there are a few workarounds we can suggest here:
1. Use an online spell checker -- perhaps you can coach the individual employee (if it's only one person) to use an online tool for this. This one is free\, and it does seem to catch both grammar and spelling issues in simple messages: https://www.online-spellcheck.com/
2. Determine what the response was in reference to\, and\, if possible\, create a snippet to handle similar questions in the future. This is the great benefit of snippets -- the language used in the response can be approved by management for both content and spelling/grammar. This will work best if the response is something that is a frequently asked question.