How to restrict only to 1 topic

How can I restrict gpt-3.5-turbo-0613 to only respond to a specific topic? I’m passing a system role prompt that should only serve as an assistant to provide information about a specific topic. I’ve included in the system prompt: “Only provide information about one topic.” But then I submit another user role prompt, “What is a dog?” and it responds to it.

Give it a clearly defined role in the system prompt. Concisely explain what its tasks are. Try to avoid negation. You can get a bit more force by repeating the key part of the instructions at the bottom of the user message.

There is a limit to what 3.5 can do, but you can get quite far with simple tasks and clear instructions.

I have added the restriction at the end of the user’s text. However, it still keeps bypassing the restriction.