I have two charged off accounts on my credit report. I have a question in regards to collections?

I am concerned about identity theft. A collection agency contacted me re: an account that was charged off that they want me to pay, but that account number does not appear on my credit report and they said it will take 4 weeks for me to get a validation of debt, which will have my name, social security number, and address on it, but not my signature. What should I do?