case nr***0. locked account

On 25th April 2015 I queried my bill and it was highlighted by the agent that bis was charged more than a year after I upgraded with 2 samsungs... A request was logged to refund me but the 1st agent logged it as I want my next payment to be settled etc.. So been trying to get the money refunded as the payment should be debited as normal... I was promised that the end of May bill will be settled and a balance of R540 was paid into my account on the 21st of May... Both my contracts are locked now as according to 8ta I failed to make payment... I apparently owe them R422. For more than 3yrs my account has been in the R900 range n failing to understandd why R422 wasnt debited if I did owe.. All the agents agreed that they can see that my account is not correct on their side and each time I have been asking someone from billings to call me... Been now almost a week that my contracts are locked... What do I have to do as no one seems to come back to me, been trying to get them to phone me since 25 of May... Quite frustrating...