Poor service and incorrect billing

I called cell c on the 24/02/2016 to make a payment arrangement and i was advised i can go and make a cash payment at the bank,and once its done i should fax or e-mail the receipt, then i went to bank and pay the money to Cell C a/c and later i e-mailed the proof of payment.The following day Cell C debit my a/c and when i call to query this i have been told that someone will call me back before close of business on the 25.02.2016 and as always no one called me back ,i then call the call center i spoke to Nkosinami who said she couldn't help me and when i ask her to speak to her superior she kept me on hold for 10 min and when she comes back she is telling me that all of the superiors are currently busy and when i ask her question she fail to answer