How can I get my Samsung F480 to turn on?

I have a Samsung F480 and it was working fine until I bought a new battery. I took the old battery out and put the new one in and charged it until full. Now my phone will not turn on, even though I put the old one back in and it charged. It won't turn on even during charging and the charging picture is on the screen. Can anyone help please? I am desperate!!!

Kathy
April 2013