Used Apple gift but debit card was charged

Hi! I recently purchased a MacBook under education and got my free gift card after the purchase in my email, I redeemed the gift card of $150 US, and ordered a case for the laptop and my phone, upon checking out I used the gift card for checkout it came up to $147.77 US and somehow my dads debit card was charged $406 EC which is the conversion from the $147.77 US we live in the Caribbean so we use Eastern Caribbean Dollar (EC) so I called apple support but they weren’t any help so I’m trying to get a little more help to get a refund back to my dad’s card cause it clearly says on the receipt that the gift card was used and claimed.