Cabcharge is still negotiating with National Australia Bank about the fate of its controversial 10 per cent fee on payments made with credit cards and bank debit cards to pay for taxi trips.Reg Kermode, the executive chair of Cabcharge, wrote in an overview of the group's December 2012 half-year result that "we are currently in discussions with our transaction acquirer, NAB."Kermode said: "We still do not believe that our products and services are impacted by the revised [Reserve Bank] surcharging standards because of the nature of [our] payments business and its unique characteristics.""Our fee is a service fee, not a surcharge."Kermode also alluded to delays in the finalisation of changes to credit card scheme rules by MasterCard and Visa that will make it "difficult to reach" a deadline of March 18.The RBA has set March 18 as the date when its amended standard on surcharging will take effect.The updated regulation gives credit card schemes the power to sanction banks that tolerate excessive surcharging by merchants on purchases made with credit cards (including scheme debit cards).In a guidance note last year, the RBA reiterated that the standard "allow[s] the card schemes to limit surcharges to 'the reasonable cost of acceptance', which includes, but is not limited to, the merchant service fee."Other "additional costs" that the RBA considers reasonable include "costs payable to other payment service providers and the "merchants' own costs related to card acceptance".Critics of Cabcharge's long-standing 10 per cent service fee believe NAB will have little option but to rein in the fee, assuming one or both of the credit card schemes insist on policing their own rules.Cabcharge, meanwhile, reported a decline in service fee income in the last half of one per cent, to A$46.1 million, a declining use of taxis and the spread of alternative payment systems in cabs.