My question involves a consumer law issue in the State of: SC

What is a bank's process when receiving a dispute of charges on a debit card? Do they need to actually speak with the vendor or the vendors bank to verify the charges? Is the onus on the debit card holder, the merchant or the merchant's bank to prove the charges are valid or not?

And if the merchant is an on line casino, or one of their offshore processors, would they really step up and validate the charges for something that is illegal?