My contract ended in April, My account went into arrears and I was told I can only close it after paying the arrear amount

My contract ended in April, My account went into arrears and I was told I can only close it after paying the arrear amount. This was paid and the Team Leader said the money would be allocated. This happened more than a month ago, I received another bill saying I am in arrears of R900 and my account cannot be closed because the money was not allocated ? More than a month later and besides the momey not being allocated I am still being billed.