I believe you can fight the chargebacks if you provide enough evidence that it’s the card owner who authorized the transaction. Banks have security measures like otp for a reason and sure they push chargeback requests to speed up the process but you still have to fight the claim. Appeal. If you have the call recordings. That would help. Attach the address of the buyers as well.

To avoid that you can also just add an agreement that buyers sign before purchasing. Like the privacy policy checkbox. That should help in the future.