Bank Of America/fia Card Services — not honoring written agreement

I was to ld to by FIA card services to make a payment of $110 to keep my account from being charged off and that they would settle my debt for $900. I told them to send me this in writing and they did. I made th e$110 payment in Feb 2008 and the settlement papers said that they would break up the $900 in 3 payments of $300. My first $300 payment was due on March 29, 2008. I called on March 28, 2008 to make the payment only to be told that the account was charged off ANYWAY. After speaking with a manager, I was told that B of A wasn't under any "obligation" to honor the agreement even though it is in writing. Needless to say, I am in the process of taking appropriate action to get this resolved.