How do I respond to a debit card chargeback?

Debit card chargebacks are not substantially different from credit card chargebacks. The proper response depends on the circumstances of the chargeback. If the merchant determines that it is erroneous or illegitimate and has evidence that can prove such a claim, it would behoove them to pursue representment. Otherwise, it would likely be best to accept the chargeback and try to prevent future chargebacks.