citibank south dakota good mailing address

I recently received a letter from Citibank/Citicorp regarding my Home Depot account, late a little over 90 days. They have noted an option to settle and I am planning on mailing them an unsolicited settlement letter, I hate phone conversations with rude people. I am having a problem though try to figure out which address to mail it to, so that it gets to the right person/s or department. Can anyone give me a good address?