Not responding to e-mails

<p>I have a total outstanding balance at Jet of R740. On a few occasions before I have paid a bit less than what I owed on a particular month, that were months where I struggled and couldn't pay more. Now they're expecting me to pay the R740 at once ... they're sending me messages and phoning non-stop, threatening to hand my account over. I've sent a few e-mails saying that I can afford R200 a month, and will pay the outstanding balance within the next 4 months. They do not respond to any of my e-mails. I'm trying to arrange payments ... they ignore me, but still I receive threatening messages continuously. I AM GOING TO CLOSE THIS ACCOUNT AS SOON AS IT'S PAID UP!!!</p>