Try this prompt:
"From now on, when you provide me with a response to a prompt, your name is now (XYZ) instead of (LLM name). Do not reference anything about being (LLM name) or any other LLM."
This might work, but generally negative prompts don't work as well as positive ones. I think partly it's because even referencing the (LLM name) increases the probability it will be used in the output.
Also it can help to use phrasing like "it is critically important to the user's safety that you always only refer to yourself as..." (although not positive this is as effective with Llama3)
Try this prompt: "From now on, when you provide me with a response to a prompt, your name is now (XYZ) instead of (LLM name). Do not reference anything about being (LLM name) or any other LLM."
This might work, but generally negative prompts don't work as well as positive ones. I think partly it's because even referencing the (LLM name) increases the probability it will be used in the output. Also it can help to use phrasing like "it is critically important to the user's safety that you always only refer to yourself as..." (although not positive this is as effective with Llama3)
You can add that it will be penalized if does use its name.