When the card is authorizing, I believe the fund authorization is separate then the card chip authentication. There might be a "preauth", but because there is an "EMV Error", the transactions is canceled. EMV error is different then a "card decline", make sure the chip is clean and try again. Not all declines transactions are a bank issue, some are system limits.
This sounds like your customer is using a debit card to pay at the pump. Companies that issue the card will take out a large amount for pre authorisation as they do not know how much the customer will use. We have stickers on our pumps that say do NOT use a debit card at the pump and to come to the window to pay to avoid pre-authorizations. This will not happen with a regular credit card. If the customer still insists that $150 was taken out of their card, do a reciept reprint and when you pull up the pump number that will show if anything was actually taken out.