Overcharged

Last week I went to a cell c outlet in Randburg trying to apply for a data contract they we promting and I left the store without taking it because I was not happy with their connection fee. The following day I called cell c's customer service and their agent assured me that I am going to get what I was looking for without any extra amount, I asked him a couple of times that there won't be any extra monies that I will have to pay and he said no, the deal is for R149 and I received my sim card on Monday of which its suppose to be calculated on pro rata for the first month since it is not the full month. Pro rata for R149 should be definitely less but to my surprise this morning when I saw that I was debited R294,95, what upsets me the most is that I asked their agent a couple of times if there won't any extra monies to be paid and based on that it's either I've been overcharged or someone **** to me.