Charged R900 for what?

On 27 Jan I visited Telkom Cape Gate for a sim swap. Unrelated, I asked how I can increase my present LTE 10GB contract, since I was running out of data. I was then informed that since my contract was 27 months old they can upgrade it to a Smartbroadband wireless 20GB contract at no cost, and at the same monthly fee (R399). I completed the paperwork, received the invoice (which stated amount payable is R0.00) and all was fine. The salesperson told me halfway through the transaction that the system shows a R900 fee, but he will ensure they waver the fee since I am not taking a new LTE modem with the contract. When I got my invoice, a R900 Migration Fee was added, and after numerous mails I was basically told shut up, sit down, and pay the fee! I will cancel this debit order every time Telkom attempts to put it through. I WAS TOLD NO EXTRA FEES WOULD NEED TO BE PAID! This is ****************, your salespeople should know what is going on, I base my decisions on information they supply to me! Otherwise I would not have changed this contract! Ref ***4