Device fees (Charged double)

On Saturday, 30 November 2019, I app**** for an upgrade contract on my Huawei Nova 5T. Sunday 8th December 2019, I received my first invoice detailing a double bill that will be payable at the end of December. I phoned Telkom's accounts department to query this, noting that I only had the device for a day in November, to why am I being charged the full device fee for both November and December? The answer: data is pro-rated, device fees are NOT pro-rated. I was then advised to call the store and discuss this with the consultant who sold me the contract / Rebecca. I then tried explaining this to her asking why I should pay the full device amount for November, if I'd just waited a day I would not have had to. I asked her what value I'd received for my device. Of course she had no answers, and couldn't even put me through to her manager. My biggest concern is she didn't even bother to warn me about this, only interested in making commission. I was only told about my data being pro-rated (which it was). How do they charge their clients a full month's device fee for only one day of use?