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What to do if you receive a chargeback:
1.Log in to your PayPal account.
2.Go to the Resolution Center.
3.Respond to the chargeback notice or (check on the status of an existing one).
4.Provide PayPal with the information relating to the chargeback, including all transaction records (such as proof of shipment).
5.The PayPal chargeback specialist will then dispute the chargeback on your behalf and try to recover your funds from the buyer's credit card company.
6.If the credit card company decides in your favor, the buyer will be charged for the transaction and you'll get your money back.
7.If the decision is in favor of the buyer, the transaction will be cancelled and the buyer will receive a full refund.
It's PayPal's mission to help you resolve the dispute as quickly and painlessly as possible, but the process can be lengthy, so you'll need to be patient. It typically takes 30 days for PayPal to dispute the chargeback, and it may take your buyer's credit card company up to 75 days to resolve a chargeback and come to a final decision.
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So I would gather all of the information that you have about the transaction, if this was via paypal, also as Trinket mentioned how you word it is going to be key.