Customer not informed of cost of the product - TCF Act and CPA not adhered to

On the 08th of October at 14:30pm my mum contacted the Sales department to request for a wireless landline. The consultant she spoke to was Blessing. She asked him if there were any additional costs involved and he informed her that there weren't any and that she would pay the exact same amount that she has always been paying, R117 to R125. When she received her bill for this month she saw that she owes R907. 60. She called the call center to enquire about the amount and she was informed that she was placed on the unlimited package. Blessing did not inform my mother about this package or the costs involved. She was informed that she would need to log a call with the sales department for a downgrade, REF 393776, and then log a call to dispute the amount, REF ***2. The bill was due on the 27th of Nov and she has not gotten any feedback, therefore she cannot be held liable should the account go into arrears. Blessing did not adhere to the Treating Customers Fairly Act. My mother is a pensioner and does not have R907.60 laying around to pay for a telephone bill she did not agree to.