Cell C *****ing Data. Insulting Customer Service

My contract ended recently (17 May 2015) and I had around 1.5 GB data left on my phone but when I checked one morning I had no data and a bill of R 34. My contract doesn't specify that I lose data when it ends and I still have Free SMS's.<br> <br> I contacted the call centre to query this and the person who answered me was extremely rude. I kept telling him that I had at least 1.5 GB left and he was insistent that I had left my phone on overnight and an automatic update caused this loss of data. I told him \I'm in Computer Science I know what I'm doing