Data bundles disappear from my account

I am very upset with the call centre because they are ***********. I was surprised to buy 1GB of data on a Monday and it disappears on a Tuesday. When I bought the data I got an additional 1 GB. Normally 2GB of data lasts me a week. To top it all, MTN gives me 300MB of data on the 21st of each month. I received the notification but when I looked at the balance it said, I have no data zero. But a second ago they said they have transferred my monthly 300MB of data. To my surprise even the 2GB I had had disappeared. I spoke to Vuyiswa Kubeka who was useless and just told me her supervisor that refused to come to the phone says. if it's not there then I have used all of it. I asked her if the 300MB I got after notification and I look at the balance and it said zero when did I use it all? She said I used it even if it was a second. The supervisor never called me back like they promised, Simon Sogo. Then I got a call from the data bundle department, Fred. He said he will call and explain how I may have used it but no work from him since till today. I just feel MTN is cheating its costumers. Period!! They still have not given proof what I spent it on. Waiting...