How can I contact the person that disputes this payment, and get my money back?
here is a guide on how to proceed when a chargeback is filed. there will be a notification on your square dashboard as what to do next.https://squareup.com/dashboard/
https://squareup.com/help/us/en/article/3882-resolving-payment-disputes
Looking for other merchants that have had EMV Disputes Responses denied by Square, it is a violation of VISA 10.1 for a processor to deny a merchant the right to respond to an alleged EMV Dispute. VISA 10.1 is very clear that the cardholder must be able to prove a multiple prong test for the dispute to survive. If the cardholder claims they did not authorize or participate in the transaction, but actually provided you the card to swipe the Dispute is dead on it's face, Secondly VISA firmly states for the claim of counterfeit card the card must have been reported lost, stolen or counterfeit prior to the transaction date, third the cardholder has to prove the card was a chip card, fourth the cardholder must prove that the card was not used at a chip machine. At if anytime the cardholder can not prove any of these prongs the dispute is DEAD. If Square has denied you the opportunity to respond to an EMV Dispute, please contact me. It is against VISA Regulations for a cardholder to knowingly charged and then dispute a valid charge, it is also a violation of VISA Regulations for Square to deny a merchant response to ANY dispute.
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