try to get my settlement amount

I tried to get my settlement amount the first time and it was was given to me over the telephone and it was R23 000 something and asked for a letter to state it , but never received it and today i called and then they gave me an amount of R29 000 something. Now i ask why so high settlement amount and isnt someone that wants to settle their account to get some of the intrest off ????? And on the statements i got from you the amount i paid stays the same , how is that possible if i paid my account every month.