Threatening me to pay before due date

I made payment on my account on 6 July which did not reflect on my July statement. I then informed Cameron Pillay and Meeander Moodley who then found the payment and told me next payment is due on 31 July. I made payment on that day, but it was short payment. I then received threatening sms's to pay FULL amount of R70 before a certain date (again today) or I would be handed over. It is not the 31st of August so I am not sure why I have to pay the FULL amount before then. I tried to phone but the phone was put down in my ear, I mailed the two above again but no response but you are threatening me for R70??? REALLY???