Unable to help me

I had received an email requesting me to pay a minimum amount of 74.95 and my outstanding balance is X amount. I then phoned MBD on 08-07-2015 to make payment arrangement for my outstanding Truworths account, The outstanding balance then had increased in 1 day to Y amount, Today 09-07-2015 I received another email from MBD requesting payment , and guess what... THE AMOUNT HAD INCREASES AGAIN. So interest is added on a daily basis, By the end of this month I will probably owe double on the account. How is this possible? When I had Phoned yesterday the lady had told me that she would phone me back with an explanation and then help to set a debit order up. This has to be *******. adding interest on a daily basis?