What kind of response do you get?

They will pretty much laugh or they will get ticked off and sue you. That is not exactly how the debt settlement process works.

I'm not sure that letter is going to be very useful. In my experience, credit card companies have guidelines regarding what adjustments they are able to make to your account at certain delinquency points. If you are not yet delinquent, you can send them a letter which outlines your financial hardship, and some of them may offer you a temporary hardship program (in my experience, 0 to 10% interest rate, 1% minimum payment, for six to twelve months). Some of them will probably not offer you anything until your account is already delinquent, and some may never offer you a reduced payment amount. If you want to settle the account for less than the balance owed, you will probably have to be several months behind in your payments before the companies will agree to or offer a settlement amount.