I would like to get a replacement phone I just got on 3 weeks ago and I have another problem

You are not addressing Apple here. This is a user to user support forum and Apple does not participate here. If you wish to speak to Apple Support, you need to use the Contact Support link at the top of the page here. 

If you wish to get help here, you can describe the problem you are experiencing and someone can provide troubleshooting steps to try and fix the problem if possible.

Make an appointment at the Genius Bar, take it to your local authorized service provider, or call AppleCare and arrange for mail in service.