No promised refund after 4 months

They did a job or me late Jan 20. The quote was R220 call out plus R450 labour VAT included. After the job was completed, I received an invoice for R220 + R450 + R35 spares exc VAT. Total R807 plus change. I queried the VAT on the invoice against the recorded quote phone call. They sent me invoice number 2 : R250 call out + R450 labour + R35 spares exc VAT total R845 plus change. My wife paid the account thinking it was correct an amount of R845 plus change. A week later I receive invoice 3 telling me to ignore all previous invoices for R217 call out + R390 labour + R35 spares exc VAT total R740. 7 April I get an email threatening me that I did not pay. I checked all bank accounts and discovered that JNT Plumbers actually owes ME money. I sent them proo o payment of R845 plus change and received no response. After many reminders for my refund, I received an email from Wendy Sanders on 18 June asking for my banking branch code - stupid question if you are making an EFT - but nevertheless emailed the details AGAIN. Today is 06 Aug and after many reminders have still not received a penny from them. PLEASE do not use this company. The workmen were friendly but they did damage my taps. It is not worth dealing with this company accounting department. AVOID !!!