Exorbitant costs and crazy charging of interest

I have a horrible experience with MBD, I had an arrangement made to pay off my finchoice loan, which I have paid and have requested a settlement letter, but instead I am told I owe them R334, to my surprise they told me I was owing R400+ which I then paid R200 in this very month of April and now I am told I owe R334, I tried to request a statement and explanation of why the debt keeps on going up instead of down and I was told that it is because of the sms and calls, but why keep on calling me when I have settled the account and have been making payments as arranged, but I am charged on unwarranted calls. You are exorbitantly charging me interest, and communication costs when I have stuck out my arrangement and promised and have fully paid the initial debt plus interest. Please sort out this mess or send me a statement of my account and clarity on your charges. You guys take advantage of people!