Custom Prompt for Agents To Restrict outside knowledge

[sudhir-cg]

I was working on some bot with custom knowledge. I integrated langchain reAct agent with RetreivalQA as one tool for that agent where tool have its one prompt. But agent have its one prompt.
How can I pass my own prompt in it so that I can restrict Agent from giving outiside answers and answering questions like:
Who are you? Who built you? according to the content I set in prompt.
Now It gives Who are you? as I am Open AI agent. I want to answer like I am XYZ company agent.
Really grateful for your help.