I love this interesting plant, I had one already and planted a second one a few days ago. It is called the Balloon Flower or Platycodon. Balloon flower is a perfect name for this unusual flower that resembles and inflated balloon. I took the above picture on Thursday and the ones below on Friday; it is the same flower fully opened.
I've never used them as cut flowers but they are supposed to do well and be long lasting in bouquets. They have a milky sap, so the ends must be singed first. I'll have to try that sometime.