Well, remember they have relationships with both sides of the transaction: the payee and the payer. And their responsibilities are legally regulated under the Fair Credit Billing Act. So no, they are not your advocate.I've been re-reading the above responses on this thread, and the content here has inspired a somewhat philosophical question for me: Is a credit card merely a consumer convenience so that we don't need to walk around with bundles of cash and personal checks? Or, stay with me here, should a credit card company relationship with the consumer take on an element of advocacy? When the consumer pays $95/year, is that simply for the convenience or should it mean that the CC company has taken on the mantle of advocacy? Should the CC company offer its best customers--in my case, platinum card holder--an actual service beyond being the middleman for payments? In any case, Citi has been adjudicating my case (their verbiage, not mine), so it would appear that they're willing to take some responsibility for resolving the problem, which I believe is how it should be. The problem is that at this, the 11th hour, they seem to be abdicating.
Also, remember they can not decide if you actually owe the money--only whether they will pay it. Even if you win the credit card dispute, Avis can still come after you for the money via the collections process.
It's not clear to me who is "adjudicating the case": Citi's credit card unit or the car rental insurance company/administrator. Since Citi is still insisting that you pay the credit card bill, I suspect it's the latter. In this case, they may simply be investigating which charges they are obligated to pay as opposed to which you legitimately owe. It also occurs to me that since you told them the damages to the car were pre-existing, they may even be investigating whether they should have paid for the car repairs (since they are only obligated to pay for damage that resulted from your collision with the speed bump).