Double Billing

On the 23rd of May 2015 I paid my remaining balance of R142 by the amount of R150 at Nedbank Oudtshoorn and then used my number *** as REF. Then I went to the cell c store in Oudtshoorn to confirm my payment and the lady confirmed that my line was now no longer contract. Therefore the lady said I don't need to fax the proof of payment. of which I showed her and she re-affirmed me again there won't be money deducted. Now to my surprise on the 15 June 2015 I get notification that that very same amount is been deducted. I want my money back in my account as I'm fed up with this network. the whole reason I paid in advance was because I wanted to be done and not pay anymore money and close this damn line. Besides this network is useless in Oudtshoorn just like Telkom mobile.