I've changed my credit card info in paypal & is there any charge to it?

I've got my new debit/credit card so I went to change the info of my old card to the new one. Then, I received a message telling me that "the first transaction on your new card was USD1.00.." and that if this transaction was not made by me i should call the hotline. It happened right after I changed the details. So is the USD$1 charged by paypal? I don't get it!!!