Unprofessional Conduct

I have had a Chatmore 200 postpaid contract for a long while now on a month to month basis after my 24 month contract ended. I noticed on my Statement for Septemeber my contract was upgraded to Pinnacle contract . This was done without my consent either in writing or telephonically. My previous contract had a recurring data bundle of 1GB as the chatmore 200 did not have sufficient data. The new contract includes data but I am still paying for the recurring bundle as well now. I would like to understand why the contract was changed firstly at least give me the details of what your have changed my contract to so that I can understand what I am paying for and to see if it actually suitable. I am ready to cancel this contract with immediate effect if this is not rectified.