Incorrect billing and no one to speak to

My debit order bounced unknowingly to me, Vodacom then blocked my number. I went into a Vodacom store to pay up the outstanding amount and they unblocked my number. Come month end, they've now double debited me for the outstanding amount but it was already settled in the store by the Kiosk. There is NO way to get hold of anyone and Vodacom to query this. The people in-store can't help and say you need to call the billing department. This is ridiculously - how do I get my money back as you've taken too much from me