Worried customer

After complaining about builders, the branch manager called me and I explained everything. He said he will work on my complain. A week after he called again asking same question. I explained again, after that the previous manager called me and denied thar he never explained that the converter is under warranty. Seemingly they are not prepared to solve my problem. I paid 8000.00 for it. I wouldn't buy something for this amount if they told me its not under warranty. Please step in and help me.