Help with FTP permissions

Hi - I have a problem with FTP permissions that I’m sure is something simple, however I am no unix guru. The problem is when ftping sound files up to the sounds folder on my Asterisk server. I log in as user “sounds” and put my file there. This works fine the first time. But if I try to replace the file it says access denied. When I look at the file on the server it has an owner of “Asterisk”. I then have to chown and chmod the file in order to be able to overwrite it from the FTP client.

Can someone advise where I properly set the file permissions?

Thanks a lot.