I was misled by Vodacom consultant

Good morning Towards end of April I did an upgrade over the phone, I specifically told the lady who was helping me that I want a top up contact nothing but to my surprise she gave me an open contract and I was not aware of that. What makes me angry is that I told this lady that the contract is for my 9 yrs old ....so now the Lil one has over used the services I just want to know who is gonna be reliable for the bill cos I have ask for top up not open contract