So I sent GW letter to my credit union which I have been a member of for 15 years asking them to remove a few late pays from 4-5 years ago on an auto loan I paid off a couple of years ago. 2 weeks later I received a response and they stated that because they couldn't verify my signature or other identifying information that they need more information to authenticate the veracity of the request. They want a copy of my DL and a notarized statement requesting info on my account. I did include my account number and return address but I did forget to sign it. 
Has anyone had this experience?
Part of me wants to write a nice and nasty letter back to them but I know better.
Should I resend it with a copy of my DL and sign it this time? Should I just call the collector who wrote the letter?
thanks!