Penalized for unknown debits!?

So this morning I get a notification from Fnb informing me that Telkom Mobile is trying to debit me R744. I paid R499.71 for my cellphone and my LTE of R269.00 is debited. Now thanks to my payment bouncing I'm charged R110 from fnb for unpaid magtape. Telkom invoices are telling me that I am still owing R499.00? Please can someone clarify to me what the issue is as I'm being penalized for this nonsense.