very disappointing service. very disgruntled customer. Annual payments can never be simple it seems?

I am having a nightmare of a time trying to get an account manager to send me a personal email address so I can try and sort out my account. I have been informed of the amounts that are due, which I pay, then I get cut off because I have short paid... when I paid what I was told to, but it seems that each person has a different formula.... to try and explain the situation over the phone takes ages, and every time I have to try and re-explain the history of many years of problems which just leads to complete frustration. I would like to correspond in writing first, so that the account manager has the opportunity to review the history and then when they phone me it is with the correct background.