Continuous threatening messages and calls

I paid up an account which only had an outstanding amount of R939.30 on the 27th of July 2015.There are two accounts and two different reference numbers come through from the same number.I used the incorrect reference number. Minutes later I contacted them making them aware and was asked to send a mail stating the correct reference and attaching the proof of payment, which I did, this was received and read.<br> <br> Since then I have received three emails stating the following:<br> <br> -\Time is running out! Failure to pay"<br> -\""Due to non payment...legal documents prepared for court\""<br> -\""Attorneys are proceeding with sending the Sheriff\""(This for the vodacom account which is also paid up)<br> <br> After EVERY one of these messages I have called to explain the same story about it the accounts being paid up and I get told I will receive paid up letter shortly"