Charged R969 for a quote

Requested a quote for plumbing work in bathroom. Came back with a >R12 000 quote, which I did not accept as another plumber could do it for R3500. What's more, they sent me an invoice for the quote for R969. No other plumber I have ever asked for a quote (i do this often as i own several properties) have charged me. I was never informed of this charge beforehand - if i was, i would not have instructed the quote. Now they have handed me over to their debt collectors who have sent me two letters of demand and if now threatening legal action. This is totally ********* and dishonest and not consistent with standard industry practice.