This was for the green card. I was late on it and got a collection call and immediately paid it before the 30 day window. AMEX, not the CA, reported it as a paid collection anyway.

It was a really nasty CA too, can't remember the name, but I reported the CA to the FTC and everything because the woman was abusive on the phone and harassing. She called my dh (AU on my account) and told him about MY account. Hung the phone up on me and immediately called my cell phone. It was awful. Anyway, the balance was $1835. I paid it off before the 30 day notice from the CA was up. I DV'd the CA. The CA never responded and it was listed as a collection on all three of my CRs.
This was last January. So I sent a GW letter to AMEX (the address listed on my CR in Florida). It was a first try letter. I explained that I had been in a serious car accident. That my insurance companies were fighting who would pay the bills (This is true). I have excellent health insurance and excellent no fault coverage. In NY, even if someone else is at fault, your no fault insurance covers it. Well Geico, decided to be jerks about it and started denying all medical claims. Well I still needed medical care and no one was paying. The drs and hospital refused to see me unless I paid up front. I hired a lawyer to sort out the mess. Eventually my health insurance agreed to pay because I am a federal employee and the contracts are written that way, however, the damage had been done. To make it even better, after all that and arranging for my health insurance to pay for surgery, Geico went ahead and paid the bill without notifying me. I still have a suit for that because there are bills they didn't cover. Anyway, I explained the gist of this in the letter.
I told them that I had been trying to get back into their good graces. It was bad enough that I had had a car totaled, went from a 0% loan on that to a new loan with interest (will be refinancing that within the month!), and had terrible trouble with all of this even two years later. It would be really nice of them to remove the tradeline. I had also said that I had been told that I was eligible for OASIS. However, after about 20 calls, no one could get me into the program. Any help that they could give would be very much appreciated. That sometimes bad things happen to good people and that's what happened with me.
THEY TOOK IT! I thought AMEX would be really hard to gw, but my letter worked on the first ttry. So I was really excited!
All of the above is absolutely true