Overcharge by Vodacom

i have 2 cell phone contacts for SMART top up S+ contacts + other contracts. MY last invoice was for an amount of R2202.29. Invoice for May reflects R2343.29. My contacts are fixed and firm. when I queried with Vodacom, they told me that they can increased the contract which is according to their T&C is do-able, clause (5.8) . they increased my data bundle from 500mb to 650 mb and charging me extra. I'm aware that ICAS has passed a law whereby the unused must be carried over. I spoke to Fumani & Patrick at vodcom was told that the can change the contract anytime the want. According to Patrick, they have to send notification to customer 20 day prior to the increase/ change, which I did not receive. Requested to proof of notice to me and Patrick could not provide.