Account Query- frustrated

So i have been a vodacom customer for a very long time now. i had a premature cancellation in december 2017 which i paid in full and sent the documents and proof of payment as requested. i cancelled and paid on the 20th dec but vodacom still debited my account on the last day of the month, and again in Jan. when i called voda in feb i was suprised that my line is still active, th very same line i cancelled and paid off. after couple of calls the line was cancelled on the 15th Feb 2018 - now just because someone didnt do their job and decided to cancell the line in feb, i then asked them to reactivate my line as i was due for an upgrade soon. that was done but i was not informed. after speaking to 5 consultants i was assured that i wont be billed for the handset but will be billed for airtime as i already paid the cancellaltion fee. i was confused to be told that i owe vodacom , i asked how? cause i paid off and you were still debiting my account. however after numerous calls i was billed an amount of R783 which bounced back leaving me with bank charges and all. i want to know debit the amount of R783 whereas i dont owe you anything. are you employees so *********** or ******** to our complains? i cannot be calling and talking about the same issue on a monthly basis. i want my refund , i want this matter settled ASAP. I am very angry and frustrated with your services. all your consultants promised me that my account wont be billed, but how did it happen, it means someone is not doing their job. this is frustrating as i cannot get answers as to why my line was not cancelled in dec as per the email and documents sent.