Unclear Information

Yesterday I received a call from Melanie who told me about a Data Top Up plan and it seemed like a good package, I then changed my service plan to the one she was telling me about. However, today I realised that my current plan (Flexi175) is much better and cheaper. Melanie had adviced that I can change the plan at anytime, however today when I called Vodacom to switch back to the Flexi175 I was told that I can only change it in 3 months. Why am I getting different information from the same company? Please change my service plan back to the Flexi175 plan, I do not want the new plan to be implementing. Thanks.