Bad service and being **** to

I called in February to cancel my contract and change it to prepaid i spoke to an Indian lady she advised me that she will do it on a month to month contract and I can cancel it or change it at any time I've even confirmed it with her twice over the phone and she said it's correct I can change it at any point in time. Yesterday I called to change it to prepaid the lady advised me she can't because it's a new contract *** vodacom i did not agree to this is want this resolved this is not the service to give your clients by giving us false information.