Unallocated debit order payments

They keep telling me that my account is over R1,000 in arrears. I keep telling them this is not possible. Every Debit Order has gone off my account that is supposed to - I haven't missed any payments. The amount is exactly two months of my Debit Order amount. This is clearly a misallocation on their side. But whenever I phone to try and resolve it, the call drops before we can actually get anywhere.