Why is my phone gone blank screened and not turn on?

My phone was working perfectly normal, then i was walking home it was on 28 percent, and my brightness was down. I got home and tried to turn my phone of, its not turning on. Iv done almost everything to try and fix it, i'm not insured but surly i can get a claim as iv only had the phone for two months.

At first i thought some how it must of run out of charge, but its been on charge for two hours and nothing. Iv tried plugging it in to my laptop, nothing, not a peep. I held the power button down for twenty seconds and still nothing. I haven't dropped it or anything so i just don't know whats happened. Please help me. Thank you.