Paid up Account

I paid the last amount (R199)I was owing Truworths Sunday 3rd November. I paid via banking app. Later I received an sms from Truworths reminding me to make payment. I emailed their customer service and they asked for proof of payment which I emailed to them 3 weeks ago. But still to day they keep sending me sms to say that I must pay R203 I think they have added interest. I have been asking their customer care on the progress of this matter and they told me that they have sent my proof of payment to their accounts department but still nothing is resolved. I do not owe Truworths a single cent...and this is affecting my credit record. Please sort it out ASAP