Letter for permission to use song

My group have discovered the email to the record company that Joshua Radin is signed to, and have sent a letter asking for their approval of the song. So far, we have had no reply but this is not a bad thing. As long as we have asked for permission, we are legally allowed to use the song UNLESS they reply with a definite no. However, it has been a good month or so since sending the letter and we are confident that they are unlikely to write back.