THANK YOU, WHOEVER YOU ARE

I received a letter in the mail from one of my credit card companies giving me a PIN number and some information about services that they offer. However, nowhere in any of the paperwork did it actually say the name of the company who sent the letter. I copied the paperwork and returned it to the address on the return envelope with the following letter:

"Dear ???:

Thank you for your recent letter assigning me a Personal Identification Number and telling me about your AutoPay service. It is so nice of you to be thinking of me in these ways. I have copied the entire contents of your mailing (including the envelope) and enclosed it with this letter. WHO ARE YOU?!?!"