Huge bills and no response!

Last year I got two cell c data contracts. R99 per month for 2 gigs including wireless routers. My first bill was R1400! I queried it and they said that I did not put a limit on my account and that once the 2 gigs was used it just continued to bill me. So I put a cap on of R50 on both numbers. My next bill was R900! Never mind the cap I also have limited my devices to use a max of 2 gigs and I am not even close!! I sent this through to cell c on 5th January and after no response I queried it a couple of days ago again. Still no response. There is no way I used the data and am sure that cell c have made a mistake and are billing me for every bit of data used as there is no other explanation. I have even reverted to recording my data usage not only on my devices but also I write it down. I wish someone from cell c would either call and explain to me exactly what is going on but nothing. Ref number ***