The reason you should keep it short and sweet is because you want to provoke attraction. You want her to still have questions in her head about you, promoting even more future conversations. Lets face it, mystery is what keeps people wondering. When you ask a question and get an immediate answer you are then satisfied. So what i'm trying to say is when she asks you a question give her an answer but not too much, that way you promote further questions. Don't bore her with a 20 minute response ever! An easier way to tackle this is to mostly ask her stuff therefor eliminating chances to talk too much. Ask her everything, trust me girls like to talk about their self because they are their favorite thing to talk about! The other cool thing about only asking her questions is that you are in control, you hold the keys to the conversation power, you steer the ship wherever you deem it to go.
So in conclusion when it comes down to a conversation on the phone with the girl you like keep it simple and say very little. Keep your responses promoting future questions. Give half answers and then ask her more questions. You ever heard the phrase "a little goes a long way"? This is KEY! Conversations are a game so have fun with it but with this method you will always WIN! More on this topic in the future!