Misleading Information just to sign up customers

I app**** for membership for my son Nov 2023, at the time he was 16, turning 17 in December 2023, the lady gave me membership for R320.00 x 24months, i accepted. Now suddenly as he is 18, the price increased to R600.00pm, of which i am shocked, the lady was fully aware of the fact that the would be turning 18 in the next year, why did she not inform me of the price increase, then i would have only done it for 12months. Now when trying to reverse the debit order they will not accept it, and they refuse to give me a reason for this price increase. Daylight *******.