Is there an extra charge for use of a debit card?

Yes they did the same to me

I don't believe that there is. Beware of using this rental company...they are shady and added $500 more onto my bill upon return. Also added $300 onto my bill when I went to pick up after prepaying online. Shady.

They're really shady. If you change your mind about renting they charge you for two days rental anyway.!!!!!