Are premium authorised apple sellers allowed to charge a premium for battery replacements above the price quoted by Apple?

Are premium authorised apple sellers allowed to charge a premium for battery replacements above the price quoted by Apple? Also they are not taking appointments for this service. It seems that Apple should be ensuring a seamless and consistent Service standard which is clearly not happening here with Bimp Annecy. Apple quotes 29€ for battery replacement and Bimp quotes 39€. It seems that due to the battery issue in iPhone 6’s, Apple should ensure no hardship on the franchisees given the admitted battery fault. Thanks, sari