Threats

I have been receiving phone calls, emails and sms from truworths stating that I have a huge amount in arrears and demanding immediate payment of R1200. I called them back today and the lady confirmed that I only owe them R200 and could not explain to me why they are demanding R1200, she said it's the stores problem and she is in the call centre and it's seperate. I made arrangements with her regarding my next payment and since then I have received another 3 emails demanding immediate payment of R1200 and telling me I have been reported to the credit bureau. I find this unacceptable that they added a payment which is due the end of the month to my arrears and that I still receive threatening emails after I have already made an arrangement. The call centre is also useless and I have a feeling that going into the store will also be useless as this lady told me it's the stores fault and not the call centres fault. I can't get any answers from truworths regarding this.