Bluetooth tethering is sharing your phone's internet connection with the computer, that's why there is an extra charge. This is not what you want. I would go into the bluetooth settings of both your phone and computer to make sure you are not missing something. Also, an easier solution (bluetooth is unbearably slow for file transfer) may be to look into the app called AirDroid. https://play.google.com/store/apps/details?id=com.sand.airdroid&feature=search_result#?t=W251bGwsMSwxLDEsImNvbS5zYW5kLmFpcmRyb2lkIl0.
Thank you for your recommendation - I will give this a try.