Debit Order even though cancellation requested

I requested for my contract to be cancelled, received a settlement quotation and paid it on 29 December as an instant payment from my bank. I phone to inform Cell C that I have made the payment and that I want to cancel the contract immediately. The call centre agent told me that they can't see the payment and will only be back in the office on 2 Jan. I was told to call on 2 Jan, ask for Fundo and they will then credit me the debit order for January as it could not be cancelled at the time. I phoned on 2 Jan, asked for Fundo and after being sent from pillar to post was told that he will call me back. I am still waiting for the call. I took it on myself to call in again today, asked for Fundo and he is not in today, another agent asked if he could help so I explained the whole story only to be told that I am still liable for this month's debit order as I received the benefit. Well in my mind I cancelled in December and used it up to the 29th after which I switched off the LTE router permanently. I was told by Fundo that they will credit me. You can check I have not used any data this month so you can remove the benfit and give me my money back please.