MY DATA EXPIRED REALLY!!!!

Since MTN depletes data for absolutely anything, I bought myself a 2GB data budle from my own personal account so that I can have a large amount of data for the next few weeks going forward. Today I get an sms, stating my 2GB data bundle has expired! I purchased that bundle to use for at my own discretion and so that it can last for a few weeks, how do you just decide that my data has expired???? I still had a good 1.8GB left!!!! There is no right for you to decide when my data that I bought expires, and I sincerely hope someone does something about this very quickly before I find myself moving to Cell C. and they still want me to upgrade so they can shaft me for more money!! Not a chance MTN, get your act together quickly or my business will be taken elsewhere!!!!