Wrong information given and not helped now we have to go all the way to multichoice again

I went to multichoice last week Thursday with my elderly mom to get a decoder activated that was transferred to my moms name, the agent assured me that the smartcard that She had would work in the new decoder, when the dstv installer came to put on my dstv decoder today he told her that the card wont work and he also called he multichoice call centre and they confirmed that I will have to get a new card, My mom is elderly, I just gave birth and my mom lives all the way in Randfontein, now she has to come to Randburg so that we can go back to multichoice to get a new card, because the agent told us that her old card would work