Feeling Cheated :(

I am so very upset with MTN right now!! I have a MyMTN Home Unc FLTE 10Mbps FUP 500GB 2Mbps. For the past 4/5days I have not had any enjoyment out of this as we are unable to watch movies or download etc.. I have been emailing the customer care line who sent me to the coverage department. I have been told that I have reached my FUP of 400GB, I have clearly stated that my contract states I have a FUP of 500GB, this is also stated on my monthly statement, only to be told that this plan only has 400GB FUP!! so this is false advertising and I am being charged for something I am not able to use. Now that I have sent the statement to them to rectify their error, I hear nothing from them. I have in total only used 411GB and have another 89GB to use before being throttled. This is not on MTN, I have always been behind you. You were my people, don't cheat people out of their usage, please man. fix this!! I am not happy waiting another 3 working days for this investigation, you have already taken 4 days from me.