Shell

I attempted to fill my car with gas on 7/30/19 at the Georgia Ave. station. AS usual, I entered my credit card and received the response to see cashier inside. I entered the store and explained the statement to a Mr. Gentle who told me to pay him inside, which I did using the same credit card that was rejected at the pump. He then told me to return to the pump and re-insert my credit card. I protested that this might cause me to be double charged. His response was that it would not, but that it would only approve the purchase, but will not charge me again.
When I got my visa card statement, I noted that I was double charged for the purchase. So I returned to the station, showed Mr. Gentle my inside purchase receipt and my Visa card statement from my bank. Mr. Gentle refused to recognize the problem but insisted that there was no way that I could have been double charged and if I wasn't satisfied with his response that I could go online and google Shell Gas and explain the problem to Shell. I have all of my documentations, i, e., receipt for the inside purchase and my Wells Fargo bank statement. I would like to be reimbursed for the double charge which was $45.75 for the inside purchase which he told me to estimate the amount that my car would take, and and $36.66 for the actual purchase at the pump.