My HTC Thunderbolt is dead, does not power on. help.

Hello.
Couple of weeks back, I left my HTC phone with low battery power before I go to sleep. 
When I woke up in the morning, it is totally dead.  My TB turned into a brick over night.

Actions taken:
- Charged it using several chargers. Did not work.  The amber light does not appear at all.
- Plugged it to computer using USB cable, assuming that it will turn on as it usually does when you plug it in. Also did not work.
- Performed hard reset by pushing power button and volume button at the side for several seconds. It did not work.
-  Bought two new OEM batteries abroad assuming it was a faulty battery.  Did not work too.  I tested the new batteries with multimeter and they are good batteries fully charged.

I cannot call Verizon to have this replaced because I bought this used from someone and I've been using this for several months.

Does anybody have a solution on how to fix this? 
It was such a good handy phone for my internet surfing use on the go and I would really like to have it fixed.
Thanks in advance for those who can help.