Why not use: "Bernese Mtn. Dog puppies. Call xxx-xxxx."
When you answer the phone line, just say that no puppies are available at the moment, but you'll be happy to help answer any questions for them, and to help them find someone else that may have puppies currently available. Don't say you never had any available, don't say if you plan to ever breed a litter or not, you just have none available right now. Pat Long (& Luther) Berwyn PA