No return or refund service

Bought backup batteries online, delivered 2 Feb 2024, but they are not suitable. Contacted Leroy Merlin for a return and refund. They said their turnaround time is 48 hours at the most. It is now one week later, I have logged various calls and emails, without any success, the latest agent said no one from the online team has even acknowledged the ticket. I specifically asked it to be escalated as it powers my electric backup system for loadshedding. No one takes responsibility or seems to care, I have been a loyal Leroy Customer, but never realized how terrible their aftercare service is until now. Extremely disappointed and frustrated, I have no idea what to do to get this issue resolved.