Disappointed by Cell C's inconsistent service delivery

In July of this year I had an issue with Cell C which took days to resolve. I kept being sent from one department to another and back again. Until, eventually, after speaking to a manager, the issue was resolved. My next encounter with the incompetence and inconsistency of service delivery of Cell C staff was in August – although I only found that out now!! My data contract was coming to an end on 11/09 and I was told that I needed to give 30 days’ notice to cancel it. So, because the 11th of August fell on a Sunday, I wen into the store in the Golden Acre, Cape Town and they put me in touch with the call centre on the 8th. I went in a few days later to check that my request had been logged. Thankfully it had. Then, I noticed that they deducted the full amount from my account at the end of September. I found this strange since they had cancelled my contract in the middle of the month. So, I went back into the same branch on the 7th of this month and explained my situation to one of the agents. She took my ID and checked on their system. She said that she couldn’t see anything relating to my account. She said to get a bank statement as proof that they’ve deducted the money and that she would then put me in touch with the call centre and send the bank statement to them. Another agent also said the same thing. Off I went to my bank to get a (NOT FREE) statement. When I returned to the store a different agent assisted me. Without using my (NOT FREE) statement or calling the call centre, she was able to check on the system, using only my ID, what the issue was. Apparently, accounts are billed in arrears, so technically the September deduction was for August and they will be deducting the FULL amount for September at the end of October. Oh, they cancelled my account on the 08th of September, not on the 11th. When I asked why they’d be deducting the full amount, I was told that I still had access to all the data. I said that’s ridiculous because they ended my contract on the 8th, so I wouldn’t have used all that data. This is where I get really angry: She then told me that when I cancelled my contract, I should have asked them to do so at the end of the month. That way I’d have had a full month to access the data instead of just 8 days!! Why the hell had no one shared this information with me when I first went into the store to cancel my contract? Neither the store agents, nor the call centre agents mentioned any of this to me. I feel utterly cheated by Cell C and don’t believe that they should deduct the full amount since they were the ones who didn’t give me all the relevant information I needed to make an informed decision about cancelling my contract!