What are you importing the wav files into? Meridian Mail? A VPS card for a Symposium Express? A MIRAN? (Since Symposium in and of itself does not store these.)
Anyway, trot down to the local Radio Shack. There is a device that lets you record phone conversations, hooks into the handset plug, and from there to another device (like your laptop). Works fine in reverse -- playing wav file from laptop into phone for telephone-recorded type of interface. (And stop holding the laptop against the phone; it just makes people wonder if you've lost your mind!)