Maybe they should just improve their product to make it more resiliant, rather than blaming customers for thinking that 148 V is below 150 V? Not everybody buying these has a Ph.D. in physics and if it says 148 V on the label and 150 V on the other label then it's your product that has a problem, not the customer.
And no matter what happens, customer support should help the customer, not blame them.
And no matter what happens, customer support should help the customer, not blame them.