It's possible that:
* It's a specific phrase or title used within a certain context. For example, it could be a song title, a book title, or a phrase used within a specific culture or group.
* It's a misremembered phrase. It's possible that you've heard something similar to "Oui mais... non" but the actual phrase or title is different.
To help me find what you're looking for, please provide more context:
* What is "Oui mais... non" related to? (e.g., a song, a movie, a book, a specific event, etc.)
* Where did you hear this phrase? (e.g., a conversation, a movie, a book, etc.)
With more information, I can hopefully help you find the origin of "Oui mais... non."