Amount on quotation doesn't equal actual bill.

Good day, I was assisted by the vodacom store on the weekend of the 12th of August 2017 with an upgrade to my contract.. As the quotation that was given to me was something that suited my pocket, I accepted... The agent though failed to advise me that the additional phone(a data contract) was not included on the quotation .. I am very disappointed with the company that I am supporting now for a very long time.. As I work in a call center, I am unable to respond to telephone calls... What is my next step? My email address is **********