False agents

Took my car in for repairs but requested i get a qoute before anything is done.Antonette then gave me a verbal qoute nd when the invoice came it was more by R1800.When i enquired why the change she could not answer.i then spoke to manager Rushell who has done nothing to help give me answers all he is telling me is Antonette says she never called me which means i am telling lies nd i tumbsucked these amount....is this how renault robs people?