LETTER CONFIRMING BALANCE

I was contacted in 28/11/14 to inform me of the discount which was only for Dec 2014 I qualified for of which I asked a letter confirming such before I process the payment. Again I was called on 17/12/14 and again I requested the same and received no such thing. Today, I received another call when I explained my story and was asked to mail a supervisor which I did immediately. I received a call now from an agent telling me the discount no longer stands this after I have requested the letter on 2 occasions! This is a slip up from MBD! They never followed through and I have to suffer the consequences of their incompetence! I have done my part in order to settle this account of mine to get my name cleared but by MBD not doing what I asked I have to loose money which I already do not have! This is not the first time dealing with this company, I have before and I had to call numerous times asking the same questions but nobody wanted to take responsibility!!!!!! I am fuming mad!!!