Quote and invoice are worlds apart!

I can't (yet) fault the workmanship of the plumbing related work done to my bathroom shower. My reason for a low rating of the company is that the QUOTE I received, which was itemised very well (indicating that the company understood my requirement well), was an estimated R9,800. However, upon completion, I was whacked with an invoice for R19,250. Just shy of DOUBLE the quoted amount. Just not on!