Poor service from leroy merlin and market place department.

I bought a heater last month and it was faulty. I sent an email and I was told it will be escalated , and I will be called back with regard to feedback. To date.nothing has been done. I got emails and the last time I called leroy and ask to speak to Nikita, to check how far she was with ref number 923214, that she gave me. She told the person to tell me that she is on lunch, and I should respond to her email that she sends to me. I was so mad that I hang up. This morning 16 July 2024. I sent another email to them since they are quiet. No call . Nothing. I understand I lost the box and I apologized profusely for that, but fir them to be quiet, they don't care about the money that I paid. Can someone who once had similar experience, advice me on how to get my money back. Cause clearly the heater will not be exchanged.