vodacom ripoff unsuspecting customers

I purchased 250mb of data for 7 days which cost R35. I then received an sms to say that My data was activated so I pressed ok. Little did I know that at the end of the message vodacom also offered me 1gig for one day at R 15. When I called vodacom I was told they couldn't do anything about it as I accepted the offer and that I should read my messages. What a ripoff vodacom. I will definately be cancelling my contract when it expired at the end of May. After years of being a very loyal vodacom customer it's time to move on.