Unhappy Help me please!!!

I have a samsung galaxy SIII verizon (SCH-I535)
but my problem is the volume down button and safe mode, volume: the problem is don't works, i press but it don't works
but it works to enter in donwload mode and to do: Press volume down to restart.
for that works fine, but in the cwm and phone don't work, i flash official 4.1.2 I535VZWBMB1
but that don't fix the error, it's hardware problem or software? i try a rom but it still,
and for safe mode, i restart the device but it dont quit, whit flash it still, and with rom it still (i try alliance rom. for volume problem and safe mode)

help me please!! my phone is free for companies, i said that because, in some trheads they say for the company its the safe mode problem but i don't know.