U.S. chargeback rules are different. In other countries, you cannot repudiate credit card transactions that you authorized (and this applies to Mastercard/Visa, too). You need to do something else if you end up in a dispute with the merchant.
The cardholder’s contractual relationship is always with the card issuer, which is usually a bank or some other financial institution. This is no different in the US. If something on your bill seems off, you contact the one that issued it, i.e. your bank.
Viseca seems like it might actually be an issuer directly (it’s also a common model that banks only act as program managers, delegating actual issuance to a different entity) but I’m not familiar with them.
Whether your bank knows how to use them well to represent your interests is a different matter. For example, I’ve seen banks decline chargebacks against bankrupt merchants in certain countries because they were poorly advised about the legal ramifications, and other banks in the same country win the exact same kind of dispute. Lacking sufficient reading comprehension to parse the dispute rules (it’s a long PDF!) also seems common.