I think my samsung sgh-t819 got wet, first thing that happened is it would not hang up when i finished my last call on it, so i took battery out to restart it. when i got battery back in the only thing the screen says is "download"

you can contact the mobile service provider.....

First you need samsung sgh t819 unlock code for your original network provider. You can get samsung unlock code from your network provider or you can buy from third party sites. Then you will get details instruction from them how to insert that unlock code in your phone.

You can download your samsung themes from http://phone.mobiles24.com
http://www.mobilerated.com/samsung-sgh-t819-games.html

My phone did this a few times as well. It went on for a few days, I couldn't answer my phone unless it was closed and I slid it open, couldn't look at text messages, nothing. Finally it died and I recharged it and it started working again.
Later on the phone also would act like I was randomly opening it, so it would light up, causing the battery to die faster. Once it died completely I charged it and it worked fine again. So far it's been a month and it hasn't happened again. Now though my phone stops working where I can't receive calls or text or make calls or send texts. This can last for 20 minutes to 3 hours at a time. I can't wait to get a new phone!!!

http://www.fixya.com/support/r3771170-phone_water_damage

how can i unlock samsung SGH- T819

your battery in your phone is worn out.
go to your local cell phone shop and buy a new one..
charge it up and your set

Give it a week to fully dry out. If it doesn't work then it will never work again. Cleanliness is next to Godliness but ................................

i have mobile samsung T-mobile SGH-T819.
how to unlock
it came from usa.