I'm in a dispute with an online casino. They say they deposited money back into my VISA account, my bank says they didn't. I have no reason to believe that they actually didn't, I think it is quite likely an accounting or transmission error of some sort, as they have given me no trouble in the past. At what point do I involve VISA with a disputed charge? I would rather not do that, as it can get me on a black list of bad casino customers, but what if it is an accounting error on the part of VISA?