Droid incredible phone?

Ok so, my droid incredible lcd screen went out on me last week, i have had my phone for about 6 months... the touch pad comes on and the sounds works but the screen stays black. So i opened the phone up.. looked at the little wire connections and couldn't find anything wrong.. so i thought maybe the wires were frayed... i called verizon customer service and they gladly said they would send me another phone.... BUT i opened up the phone and looked at the wires. I have never dropped the phone or got water in it, but the sales man said that if they determine that i was the cause of the malfunction i would be billed $300. I am worried they will charge me because i opened up the phone to look. If they did charge me is it possible for me to send the new phone back to them and not pay the $300?