Misleading time lines

A week before I gave birth j went to a telkom store and looked at options for a new contract as the one I had wasn't working. The agent then told me the following day that she already put it through and I can't cancel as she would loose her job if I reported it to her manager. I thought let me just try to take it and not have her without a job. I asked her if it's a 24 month contract she told me yes it was. Today when I went to get my upgrade, I get told it's only due next year as she put it though on a 36 months contract. For the price I'm paying is pathetic and I'm very unhappy about it. I need to have this issue resolved with her and she need to fix it as it was her doing not mine