Robbing and not adhering to deals advertised

I upgraded in April on A Smart M package to the Samsung S6 Smartphone. In May I decided to migrate to the Red advantage deal. Same phone available under the same deal and total deal, including the smartphone is advertised as R999 per month. Phoned the customer centre and spoke to lady who said there shouldn't be any paying because I am actually moving to a \better"package. All done and sorted. I am on Red advantage from 1 June. Come billing time"