Cheated and ****med by cancellation consultant

Phoned in to cancel my contract which had expired as my data was all of a sudden running out faster than usual, after not even using it as much. The cancellation agent gave a cheaper package with 80GB of data on 26or 27 March. He said it was because my record with them had been very good. I only received the quote in this week, after the normal premium had gone off twice already. The device arrived a month ago already. I have not used it at all as my data has been depleted since the beginning of April after barely using it. The strange thing is when I load data on my prepaid sim, it lasts much longer and I really use it. That is more than a month after speaking to the consultant. I was shocked, because the quote is not at all what we discussed. I feel cheated and ****med.

How can a seemingly reputable company do this to a client?? After so many years of being a loyal client? Where is my data disappearing to??