Your question is very general. "A customer support app" can mean many things from a faq to a case management interface.
If you 100% can not tolerate "bad" answers, only use the LLM in the front end to map the user's input onto a set of templated questions with templated answers. In the worst case, the user gets a right answer to the wrong question.
If you 100% can not tolerate "bad" answers, only use the LLM in the front end to map the user's input onto a set of templated questions with templated answers. In the worst case, the user gets a right answer to the wrong question.