Got put on the wrong package and pathetic service

Extremely disappointed in MTN. I got put on the wrong package. I app**** for R299 for 100gb but got put on R199 for 50gb. MTN is not willing to help and is saying i should go to the store since i didnt buy it from them. Store is saying they cant help either. Initially wanted to change packages but now i want to cancel cause of the pathetic service. I can imagine what would happen to new customers if theyre doing this to me and i have 4 lines with them