2 interview letters

[render]

Hi all
Me and my wife got interview letters for same day on aug 15th. Yesterday i got other letter saying that my interview date is on sep 4th. I am littlebit confusing, What to do? Do i need to go on 15th or 4th sep. I tried to call but didn't get line .
Is there anybody in same situation?
thankyou in advance

[indianium]

You must go on your first interview date.