disappearing data and poor service

I loaded 1G data and 2 days later it was depleted even thou I use Wi-Fi at work when I called for an explanation I am told about applications down loading which is untrue because my phone currently is notifying me that I have 8 applications that need updating and I could no update because I had challenges with my app store details , I was transferred from 173 to data usage and back to 173 and eventually told no one in whole of MTN could tell me what happened to my Data . I am beyond disappointed