0-5 kg for only R99. . . What a lie.

I have been using Post net for years now, and i know how the system works. Now Saturday i wanted to post a parcel that weighed 4.8 kg and the lady charged me R219.00. even after i showed her the big sign at the door stating that 0-5 kg post net to post net was R99.... she referred me to the website to look for myself. firstly, how rude!! secondly why was i charged R219 for something that was advertised for R99