HP Printer wont be replaced

Purchased HP Printer which started to make terrible noise after the first month. Sent it to Ensure IT In Durban. Printer, according to job card, was cleaned and tested. Got printer back and when starting to print, the same noise was heard. Contact Ensure as now requiring replacement but they couldn't make that decision. Over the last 3 weeks have been emailing back and forth to HP as high up as the head of service and HP CRT and they refuse to replace. They say their procedure is to rerepair and if it goes faulty again then it will be replaced. What about rights of purchase \If the supplier repairs such returned goods and the problem persists or recurs within 3 months after the repair