Midrand PostNet robbing money

Been using postnet for years, today i went to Midrand Waterfall Corner postnet and the TRAINEE there told me that my 2kg parcel was not eligible for the R99 postage. She said its R20 extra for every kg from 0kg. Does that even make sense? The poster clearly shows 0-5kg R99.00. How did she even get the job or who is training her ??????????????