Disgusting claims department

I have been emailing and calling since 3 January. I have a burst geyser and I was insured with ooba in 2018. The geyser is not 5 years old yet. To use the warranty the manufacturer wants a installation report or invoice with codes of geyser since it's on the roof and the serial numbers are no longer visible. I vet no response from ooba claims or Hollard the underwriters. Taking cold showers for days because of one document. Utterly disgusted