Odd... when ever I dealt with customer charge backs, via arbitration... We 100% had to return money if we lost the charge back,,, Furthermore if a company has too many charge backs they can have the merchant account black listed... Meaning they can no longer charge cards with those merchant accounts.
Another ironic thing is, when a customer starts a charge back case, they are almost never informed by the card issuing company (Visa, Master Card, ect.) that they will have to pay money to do this, and if they do not "win" the case they will have to pay that fee AND the original charge.
The card issuing company's are very nice to do this for customers but don't be confused, they win either way it goes.
Thankfully it sounds like you run a legit business and don't have to know all the ins and outs... I don't work for that company anymore thank God, because it's very stressful working with companies that are not so honest.