If a customer formally disputes a charge with their bank (a "chargeback"), it's handled through Stripe, which manages the bank's dispute process. You may be asked to provide evidence of the work or agreement to support your side.
For everyday disagreements with a client, message each other in the platform first — most issues are resolved that way.
RateCards isn't a party to your transactions and doesn't mediate disputes, though in some situations we may try to help. The final outcome of a chargeback is decided by the customer's bank. 8