MAKRO REFUSES TO Refund the money for a faulty invertor

GENTECH 800W HYBRID INVERTER TROLLEY. PINVERTER1 Serial No. ***. Ref No *** Bought on the 18.12.2022 and it was returned on the 31.12.2022 when it gave a signal that it is faulty by beeping. I spoke to Makro manager Basil Green and Dennis from the supplier. The manager says the supplier must give them a permission to refund, Dennis says it is Makro to decide. The supplier details: GENTECH POWER Unit 1&2, 6 Forssman Close, Barbeque Downs, Kyilami. I hope the info it is sufficient. The problem was the battery as per supplier.Now Makro does not want to process the refund they are blaming the supplier but the product was bought from Them my Dad is a pensioner and the Manager at makro is taking advantage of him