POSTNET ORMONDE

On 30/03/23 I received a quote from Postnet Ormonde for R109 for the same box I am sending today. Today 03/03/23 I went and sent the very same parcel and they charged me R169 when I asked them why???they now say they charge according to volumetric weight.The parcel was not even 2kg. Basically POSTNET is doing false advertising . How can people be ****** in broad daylight. This is nonsense. What the adverti*****t reads UNDER 5KG where does it stipulate CHARGES FOR VOLUMETRIC WEIGHT????