Some debit cards Paypals system view as credit cards.
If that has happened to you then your best bet is to give customer services a call and ask for a refund of any charges.
Click on the words "Help / Contact" at the bottom of paypals pages and use the phone option in the blue band at the top OR very bottom of page dependent on what country you are in. Scroll down past the list of help questions and click on 'Call us' bottom of that page. Log in and get the code.
When you get through don't select any options just hang on till you get transfered to an agent OR just say the word 'Agent'". In the UK its free from any landline phone.
OR have you considered contacting Customer Service via Facebook or Twitter? You can send them a personal message from their facebook or twitter pages.