mtn is now robbing its clients

I was excited to here of mtn's night express which allows you to buy 1gig of data from which you can use from 12 am to 6 am but unfortunately it's a big **** and plane ******* from them which is so disappointing. I bought this 1 gig night express for 3 nights in a row wanted to do some serious downloads only to find that after I spend only have of that data the network would stop me from connecting to the Internet saying I have insufficient data when I still have a good 500MB on my balance I thought it was a mistake the first time so I did this for two nights in a row experiencin the same problem the last time mtn stopped my connection when I had 900MB still in my account telling my I have insufficient data but every time I check my balance there was tones of data. This has also happened to my roommate who was also utterly disgusted by such ******* from mtn. I called the call centre in all the cases when this happened but none of them wanted to re-emburs me. They all were saying there is nothing they can do they logged a query of which nobody has gotten back to me. The last operator said they can only see after 2weeks. Very disgusting from mtn bad network...it's been 2 weeks since