TV technical issue

I bought online a diamond brand tv on the 24th of August 2018. On the 3rd of August the TV just stopped showing pictures and only sound was working and later on the sound also stopped. I called hificorp n1 city 4th of August and they are telling me because my TV is less than 50inch I have to bring it in at the store but the TV was delivered to me. This will be an additional cost to me which seems unfair.