shipping charges being deducted from my bank checking account instead of P.P. balance

Description

As a small time seller, but selling for many years, when I used ebay to print up a shipping label for an item I sold, the total for shipping was deducted from my PP account. In recent weeks, the shipping is now being deducted from my bank checking account. I have not changed any settings. I have written to pay pal 3 times and they have never responded – what do I need to do to change this so that shipping charges are deducted from my PP balance, and not my bank checking account.