Telkom said phone was free and then charged for it - surely not legal?

I was on a Telkom Fixed Voice Service. On 7/3/2023 a Telkom sales agent phoned me and said they were doing away with fixed landlines, and I needed to move to their Smartvoice Basic (Wireless) Service. I was told it would be on a month-by-month basis and the new telephone would be for free. I agreed to the move, went through everything again and double-checked the new telephone was free. The sales agent assured me it was as I was an existing Telkom customer. They moved me across to the Smartvoice Basic Service and on my April invoice they charged me for the new telephone! When I phoned the customer care line and explained I'd been told the phone was for free, the consultant said as I was not on a contract, I was liable for the cost of the phone and must pay it. She said there was nothing she could do for me. Surely it is not legal to say something is for free and then charge for it. Even if the sales agent had made a mistake, I feel Telkom should not have charged me for the phone as we had an agreement that it was for free. They could check this because they said they were recording the call. Also, I'm not the only person they did this to, as they did the same to my sister.