upgrade with no notification!!!!

I had taken out a 2yr modem contract with vodacom in 2012. It was due for upgrade in 2014 however I did not get any notification that I was due for an upgrade.. added to that vodacom automatically upgraded my contract from 2gb Daytime and 2gb night owl to 3gb daytime and nightowl and they started debiting me more for this new upgrade that they had done without my permission. This weekend when I finally had a chance to go in to the vodacom store in gateway I was told that I needed to pay R150 admin fees for an upgrade on my modem however I could not understand why I had to pay girvthis as they had taken the liberty to upgrade my contract without me knowing and they then charged me for the new price for the upgraded contract without me knowing. Why should I now pay admin fees for something they already did? It isnt by any means legal as no one is allowed to upgrade you without your knowledge. I didn't even receive a new modem when they automatically upgraded me but when I went in to claim my new modem for my new contract I was expected to pay admin fees yet it was the same contract that they upgraded me to all I needed was a new modem that I was already paying the price for.