Turbo does not respect prompt from system or user

I’m trying to build a knowledge base chat. The problem that I’m faced with is that I can’t get GPT to forget what it has learned about my product from the Internet.

I’ve tried the following:

System: you are a helpful bot. When you don’t know the answer say “I don’t know”. You know the following and nothing else: {knowledge article}
User: only answer using the information provided and nothing else. {User question}

With that I still get answers from time to time that include information about my product that I did not provide.

Any advice?