WD Installations failure to repay funds

In June 2015 the owner of this business installed a geyser in my property and gave me a 5 year guarantee. In early April of this year the geyser burst and I contacted W. ****inson to advise. He came to check the geyser and it was discovered that a 2nd hand geyser had been fitted, the date being October 2007. Mr. ****son offered to replace the geyser but told me he didn't have money to buy the geyser. I purchased the geyser and it was fitted on 18 April, 2018. Despite numerous phone calls and messages the cost of the geyser has not been reimbursed and my calls and messages are now being ignored.