Penalty Fee Disputes

Im having a bad experience with vodacom where they're are unable to assist with their fault there's an amount of R200.22 of a penalty fee that was added on the account which is their fault from the sales team I was not advised to pay a prorata amount that has escalated the account to arrears and im not willing to pay penalty fee but willing to pay pro rata amount and my subscription for the current month . I called last week but the resolution was in their favor