Steam support says they have "banned" my credit card but won't give me any information

tldr: has anyone else had a credit card banned from steam? any tips for dealing with it besides use a different card or different payment method?

a few steam purchases ago, i got “An unexpected error has occurred. Your purchase has not been completed. Please contact Steam Support.” so i contacted steam support. i was trying to pay with my visa credit card as i have every single other time i've bought a game on steam before this error started coming up. steam is the only place that has any issue with my credit card and i have actually completed my purchases during this sale (and the one previous purchase) using that same credit card through paypal (which is much less convenient).

i feel like i have more questions than answers. so far i've had three very short responses from a support tech and have learned only these few things:

1. my "payment instrument" has been "banned" for "unauthorized use." that didn't tell me much beyond "yep, there's an error."
2. steam support "cannot" fix this. this one in particular makes no sense to me. why did steam tell me to contact support if all they want to do is confirm there's an error and i can't use my card? who else could fix it when only steam is affected?
3. the "unauthorized use" is not my one failed purchase where i hadn't updated my card's expiration date in steam. this is a little scary since that's the only thing that's happened with my card that's anywhere near unauthorized use, since the credit card company of course declined it because the expiration date had changed. so . . . this means someone else tried to use my credit card number with steam, but steam support won't tell me anything at all about that. it seems to have happened around the time i got sent a new credit card with the same number but new expiration date and cvv2, so hopefully that's enough to prevent whoever that was from actually charging anything to my card.

i still have access to my steam account so this is really just an annoyance. i only have 2 credit cards and the one they've banned is the one i get rewards through, so i'd rather not use the other one. i suppose i could buy myself steam gift cards with my rewards credit card (or my other card, which gets me a discount at a specific store that happens to sell steam gift cards), otherwise i'm stuck going through paypal and trying not to let it trick me into using my bank account instead of my credit card.

i probably shouldn't have expected much different even though the error message suggested i contact steam support, but steam support has been very unhelpful. if anyone's been through a similar experience and has any advice i'd appreciate it. i'm in the US in case that makes a difference. thanks for reading about my troubles with steam support!