It’s hard to tell why you ran into such a problem without seeing how you prompted but I can offer a few pointers. Use the OpenAI playground instead of chat, it allows you to specify the system prompt and edit the conversation before each submission. System prompt is good for providing general context, tools and options but you absolutely must provide a few example interactions in the conversation. Even just two prompt and response pairs will strongly influence the rest of the conversation. You can use that to shape the responses however you like and it focuses the model on the task at hand. If you get a bad response, delete or edit it. Bad examples beget more bad responses.