Voucher Advance Payment

i have been a very loyal client in vodacom for so many years i had 3 contract with them but the way they treated me is terrible. initially when my 3 contract was still existing i got a call from vodacom stating that they will offer me a free 1g data for being a loyal client only to find out 2 months later that they have been charging me for that and i closed 2 of my contact and had 1 left. on the number that is currently on contact i took an advance voucher of which they debited the amount that was due to them on the 24 October, however i have been receiving sms's stating that my payment is outstanding and vodacom has been coming into my bank account trying to debit the very same amount that was already paid and the bank has been charging me for all unsuccessful transaction and i am currently sitting on a negative balance on my bank because of all the unsuccessful debit orders that vodacom has been doing in my bank for more than 5 times . i have contacted vodacom since the 25 October until today ,even sent my statement but i have never received assistance but instead everyday Vodacom comes into my bank account to try and debit the very same amount of money that was paid already. i have been transferred from Pillar to post and no one has assisted me, the First agent that was assigned to my query *** closed it without resolving it, the 2nd query was logged *** but no one has attended to it. i am so angry and very frustrated having to deal with this every day, i sit on the phone for an hour morethan 5 times a day but no assistance, what frustrate me even more is the fact that they keep coming into my bank and the bank is charging me for that. i regret using vodacom, i am closing this contract as well because the service experience is terrible.