Converting Currency For No Reason

Recently, for no apparent reason, PayPal converted the ebay charge for a purchase from USD to CAD and debited my Visa in CAD.  The purchase was cancelled by the Vendor because they could not meet my delivery deadline. The credit to my Visa was also converted to CAD.
 
The selling price on ebay was in USD.  My Visa is a USD card with a billing address in TX. The address for my PayPal account is the same TX address.
There was no valid reason for PayPal to convert the charge to CAD.
 
As would be expected, Visa charged exchange on both transactions with a net difference of $7.45. As this cost was due solely to PayPal erroneously converting the invoice and credit amounts to CAD, I requested reimbursement, which PayPal refused.  After numerous emails they finally stated that "PayPal does not reimburse amounts that they do not charge"
 
Any help in directing my request for reimbursement to somebody in authority at PayPal will be appreciated

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