Vodacom Poor Upload Speed in Various Areas

Vodacom Upload speeds have a problem in several areas. I bought a 100GB Package and tried it in Centurion, Fourways/Sandton and in Mosselbay and Carltonville (Small Town). All these areas Downloads are fine e.g Centurion 338Mbps Down, but 4-8Mbps Upload speed ? This is not a problem on my router or setup otherwise downloads would have been an issue as well. My main area is Centurion and this is a router used to travel and upload documents and videos to the internet. Why is the Upload speed so poor in several areas ?