False advertising

Ive just been to Postnet Silverlakes (Pretoria) to courier a package (that is less than 5kgs).

I was charged R105 for package, instead of R99 as per website. When I queried price, I was told postnet head office allows postnet stores to vary pricing between R99.00 to R110 for packages less than 5kg. SIliverlakes store charges R105.00 as minimum price.

However Postnet website clearly states R99incl for less than 5 kgs. Why is Postnet stores allowed to vary pricing when website says R99.00?

This is false advertising to me.