False advertising - Joining special

Virgin Active is debiting me for the full amount even though i was told that i will be paying less for the first three months. I was supposed to pay R287 end of June, R246 end of July, R246 end of August and then start paying the full membership fee thereafter but that is not the case as virgin active has been debiting full amount from end of June. I am not happy as this is false advertising and i joined knowing i will start paying full amount from end of september.