Worst Cellular Company Ever!

In February I wanted to close my account and was given an amount of R657 to pay and I did and emailed a proof of payment and then in March I received an invoice saying I owe R279 after contacting their facebook page and their call centre contacting me there after I was told that the R279 was for Febs installment as it was not included in the settlement amount. I paid the amount and emailed proof payment on 24th March and now I received a letter of demand via email from them saying I owe them money but not how much and their call centre just rings and rings, no wonder this company closed down, I have no other way of contacting them if anyone can help me please do as I am beyond fed up with this down right despicable company.