As we don't have all the details, it's just a guess that the person who paid you used the Send Money option and choose "Goods and Services". When this option is selected, you the receiver will be charged the standard transaction processing fee (2.9% + $.30 on the total amount assuming this is a US Account). You can refund the money to the sender and get the 2.9% back, I believe that PayPal retains the $.30. And you would have to ask the sender to resend the money using the "Friends and Family" option as there are no fees assuming both accounts are in the same country and the sender uses funds from either their PayPal Account Balance or their bank account. Note it may take a week plus for the funds to be returned to the sender.
