Debited double

My debit order bounced last month. i then paid the arrears amount in via internet banking after speaking to a consultant. i realised i had put in the wrong reference and then contacted their accounts again . i was told to send the pop to pop@vodacom .co.za gving the correct reference. a few days went by and i started getting calls that y account was still in arrears. i called in again and explained the situation that i paid it already. i was told to send the pop to ********** which i did. a few days after that i received calls to say my account is still in arrears. i called in again and asked to put through to a supervisor which they did. she told me to send the pop directly to her ********** .shortly after that i received an sms notification saying that my payment was received. a few days later i started receiving the calls AGAIN!!!!!! i called in twice after that and still not resolved !!!....It is now the new month and vodacom has taken double the money !!!!How can they take double the amount even though i paid in the arrears amount last month .i have been a vodacom customer since 2006 and always held them in high regard....not anymore !!!!!!!!