Vodacom
Service complain

I have a contract with vodacom so i set up a limit of R50 so i dont run up a bill today i contact the customer service to check my usage the lady i spoke too tells me i went over with R600 i dont understand how it would get up to R600 if my limit is only R50 i would understand max of R200.What is the point of setting a limit if this function does not work for the customer i feel cheated on as this works every month now i feel like it works when they want it to work and when they want to increase their revenue it does not work