Billing 2 month in arrears... For what did I pay the first month then???????

Holding the line for 15min to cancel my contract is not good service Cell C. One of the consultants informed me that I have to pay my contract for one month extra. PLEASE TAKE NOTE: My contract expired June 2018, I have a month to month contract. So i questioned this one more month payment and the consultant informed me that Cell C payment work 2 months behind. So I'm paying end August for June benefit. So please help me with my next question. For what did I pay for when I first received my contract and had to make payment end of that month, should your payments work 2 month in arrears. I have been trying to sort this out over the phone 05/08/2019 after being transferred and call being dropped. I have phoned again this time asking for Legal department, and have been holding the line for 20 min SERIOUSLY..... I want a good explanation for this 2 months back billing.....I'm not letting this go, this has been my 4 contract cancelled with Cell C and not I understand that for 3 other contracts you have been robbing the people. Nice Cell C