Kyzmet - I had luck with Sears but I didn't write a letter, I actually called and spoke with a CSR, explained what I was asking and got transferred. Incidentally I think I got transferred to Fraud which was not the correct department and the gentleman I spoke to said that he doesn't know why I got transferred to him. Fortunately he went ahead and deleted my late payment anyway. Maybe you could ask for Fraud and claim innocence when you get to that extension.
I gave it a few weeks, disputed my CRs, and they're all off.
Keep in mind that really, this only raised my score 2 points. But with all the other negative things on my report, and the fact that I'm trying to get my first mortgage, every little bit helps.