Incorrectly billed with no explaination after cancelling contract

Good day,

I have cancelled my contract two months ago after I was notified that my contract expires on which day and when will I be allowed to cancel it. I waited for the correct dated and proceeded as required to. Two months down the line two deductions have gone off my account to the amount of R140, 71 on each month. The initial one I thought maybe was for cancellation fee but receiving it for the 2nd month has pushed me off the limits. I have contacted the pre paid where I spoke to Nokuthula who informed me that the contract department would be able to assist me. I was then transferred to Nokubonga in the contract department. She pulled out my details and informed me that my details and statement is blink and they are unable to see the transactions that is going off my account. I want the statement and reason as to why I have been billed twice and there is no proof of it on the MTN system and the reason why I am still billed after following the cancellation procedure that MTN uses. I am disgusted at this level of service. Ref on my statement is MTN SPA514778 FOR THE AMOUNT OF R140,71.