Charge off with HSBC wont take off credit report. Policies?

So, I've done a lot of research on the charge-off situation to best enable my chances to get it removed off my report. My original creditor is HSBC for a credit card (small balance). As with most, the debt has been sold to a collection agency as of January '11. I spoke with the people at HSBC, trying to get them to come around to take back the account from the CA, and then do a pay for deletion. They said it wasn't in their company policies to do so. I spoke with a supervisor as well, as I'm adamant about getting this taken off... and I'm truly at a wall now. I was going to pay in full (charges, interest, and all). They said their is nothing they can do about the credit report... they "reported history and history cannot be changed". I asked if we could change it to a "Paid" or "Paid as agreed" status. Same thing--nothing can be changed, according to them. I doubt I'm going to have a problem with the CA--I understand the PFD is relatively easy with them, but I have the original charge off on my account. In addition, I considered doing the debt validation letter with HSBC, then sending a PFD to them (but I assume it will be the same results with a longer processing period).

1. I would be interested in knowing from those who have experienced this/have better knowledge—is this false that they can’t change the charge-off once off their books and sold to another company?

2. This debt has been outstanding for some time (over 1 year). Is there a difference between the CA getting management over the collection, and then them completely selling the debt off to the point where they (the original creditor) have no legal jurisdiction to take this charge off off/change the reporting? I know this had been pushed through a few different CAs. I’m just wondering if people have been able to do these PFDs/alterations, why am I not able to do it specifically?

3. Under what conditions have people been able to get their creditors to take back the account from the CAs? (Institution, length of time, etc).

4. Is removing a charge-off contrary to the Fair Credit Reporting Act? Is it impossible to get a charge off taken off by a large institution?

5. Those of you who have had charge-offs taken off the report (not with the CA—the original creditor), what companies were these with? Were they large banks? Did they have policies in hand to do PFD? Was there significant pushback with this?

Any input and anectodal info would provide great color on this.