Matrix Complaint

On the 20th May 2023 we went to Matrix Alberton to purchase an Inverter. We were told that the KOOL ENERGY 1KVA 100AH BATTERY is the best on the market and that we would not regret it. On the 26th September 2023, the battery stopped charging and I took it in to Matrix Alberton on the 28th September 2023. I was told that it is still under warranty and the battery would be replaced. I received the inverter back on about the 5th or 6th October 2023. I plugged it in at home again and phoned technical at Matrix to confirm the settings. All went well, until the 15th March 2024,when after 2 hours, the inverter went off. I took it in on the 16th March 2024 and spoke to a manager (can't remember her name, but she had long blond hair) who told me that it will be done under a NEW warranty. This was also recorded as such on the paperwork. On the 27th March 2024,i phoned the store and spoke to Leonie, who said that now all of a sudden I have to pay R4000 and odd rand for a new battery. I asked her why did the manager then say that it is under warranty? I am not happy with this and would appreciate a resolution to this. My question was how do I know a new battery is installed and not just a recharged battery? And if it was a new battery, why is the warranty not accepted, even though your technician and manager said it was.