Quoted one price for a repair and Over Charged

JEG Diesel have had our Mercedes Benz for one month.We were quoted around R5000 for the intended repairs. When the invoice came the costs due was R10111.80 We were advised that all conversations were recorded. Once the recording was verified a new invoice would be issued. The new invoice came advising us that JEG Diesel did not have a chance to listen to the recordings, but offer us discount of half of the VAT (7%)<br> New total due R9490.90 We have no choice but pay, as the car would only be released once payment has been received. Mr Daniel Costa your customers are not being treated fairly, please advise what you are going to do about this!!!