Unauthorised incress to cellphone contract

I have had R56.53 added to cellphone contract monthly which is not as agreed with the amount that i signed up for.

The lady at Vodacom call center told me that its due to the Icasa ruling.

The rulling dose not say anything or allow for any levies or added rates or anything to that natur to be added to my bill.

This is not inline with my agreed contract amount that i agreed with so i would like to know from vodacom if they think this is ethical to do something like this?