To make it a complete sentence, you would need to add the language they speak. For example:
* "I didn't know that you spoke English." (ne savais pas que vous parliez anglais)
* "I didn't know that you spoke French." (ne savais pas que vous parliez français)
* "I didn't know that you spoke Spanish." (ne savais pas que vous parliez espagnol)
Let me know if you have any other French phrases you'd like translated!