Poor customer service

I purchased an iStar 43" TV during a Black Friday promotion and paid in cash.

Approximately three weeks ago, the TV started malfunctioning. It plays normally for about 30 seconds, after which the screen goes completely black while the device remains on.

I returned the TV to the store requesting a repair or replacement, as the issue appears to be a technical fault. However, I was informed that the damage was due to "customer negligence" and that they would not be able to assist me further.

I strongly disagree with this assessment, as the TV has been used under normal household conditions and has not been mishandled in any way. I believe this is a product defect and not a result of negligence.

I am requesting a fair resolution, either through repair, replacement, or another appropriate remedy in line with consumer protection regulations.