How can I prove a customer's fraud charge is false?

hi! someone has pretended their order was fraudulent when they placed the order and received the item. in the description, it says order ships in 2 weeks, and I missed the Shopify protection by 1 day exactly.

because the customer has their phone number on the order I texted them asking if they had purchased the item and received the order. attached are screen shots of our conversation. not only was the order delivered, but I will be charged an extra $15 by Shopify for the charge. how do I prove this is fraudulent ?