Vodacom Charge Incorrect Prices for Contract!!!

On 1st November 2015, we had gone to Vodacom to see what phones they have since my husband needed a new phone. The consultant told us that they had the Sony Xperia Z5 in stock and that they had no brochure for prices, but that the contract on uChoose flexi 200 is R550. This past weekend we went to buy a cover for the phone and discovered that the phone is actually R500 on Uchoose Flexi 200 and you get a free gift, none of which was given to us. I did ask the consultant about the free gift because i know that Vodacom had advertised that there is a free gift when you pre order the phone. so basically we are paying R50 extra a month for a contract, that was actually supposed to be R500, and if they were not sure about the prices at the time they had sold it to us then why did sell it? we would have waited the extra week if we had known.