We're sorry if you've been charged more than you were expecting. The most common reason is that the promo code you used may not apply to all the items in your basket. There are certain exclusions so please review the T&C's that were included when you were sent the code.
We can't refund discounts that haven't been used when ordering so it's best to confirm the amount is correct before placing your order. Please contact our team if you still believe you've been overcharged.