What are my rights for false collection notice past the thirty days?

I received a notice from AFNI Collections stating that I owe money on an account I never had. I did not see the letter until today, it must have gotten lost in the mounds of junk mail I receive. Can I still write a letter disputing it, even though it is past the thirty days? What course of action should I take to resolve this. I have read many complaints about fraud with this company.What are my rights for false collection notice past the thirty days?
Yes, you need to contact both the collection agency and the company that they are collecting for and file a dispute, you should also contact the 3 credit reporting companies and place a flag on your account since more than likely your identity has been compromised. Check your credit if they hit you once they might have hit you more and you just don't know about it. You might also want to file a police report. GOOD LUCK