DATA GONE MISSING

I have been a customer of MTN for approximately 20 years and have had a 3G data bundle / laptop deal for approximately 6 years. I had to upgrade in October 2014 which proved to be difficult as every time I chose a product they were out of stock. Eventually in February 2014 I managed to obtain a laptop and 3G data package - 5GB on day and night express. The upgrade was done on 8 February 2015. By Friday 13 February my entire upgraded 5GB had disappeared - not used at all by myself. MTN switched off my connection. I laid a complaint and they said they could not see where the data had gone and gave me another 2GB. By Tuesday 17 February this 2GB had also disappeared. I struggled all day Monday and Tuesday and Wednesday to get through. Eventually on 18 Feb a call was logged and a further 2GB was given to me. By Thursday 19 Feb this 2GB had vanished as well. I have been using my phone as a hotspot and only use 10MB a day... MTN cannot answer me where my data has gone and keep advising an investigation has to be done. The point is my data is vanishing and nobody at MTN will tell me where it has gone - if it is being hacked - as I am NOT using this data. Noone helps!