It sounds like another company TRYING to get you into debt via scamming. Ignore them, especially if your credit is great. Unfortunately in today's society, great credit is rare, so do your best to protect it! Don't hand out any personal information to companies such as this, or over the internet.
allied interstate is a Minnesota-based collections agency. Ask them what debt they are after, if any, and ask them to validate it via email.
Also, if they are harassing you, keep in mind you can report them to the FTC!
www.ftc.gov