Overbilling

Hi! My name is ntakadzeni manwadu. And i am here with a complaint. Ever since i upgraded my contract i have been overbilled. Every month theres high bill which i do not understand. The app shows R240 and somehow im owing more. At this point i wonder if theres something fishy going on because on the app you dont show that large amount. How am i owing so much money? It doesnt make sense anymore. At this point i dont know what to do. I have been writing so many reviews but i am not getting assistance.