Cancel contract with cell c

I went to the Cell c shop in Brits mall a month before my contract expire to find out what I need to do to go over to a pay as you go. The agent at the store told me that my contract will expire on the 18th of April 2015 and gave me a number to phone and an option to select and then somebody will assist me and change the contract to pay as you go. He did not tell me that I need to give a month notice. I phoned the number today the 22nd of April 2015 to cancel my contract with cell c because the signal at my farm is very bad and they told me that they can't do anything about that' just to find out that I still need to give a month notice. This means that the contract is 25 months and not 24 months and I still need to sit without signal for another month. This is very poor service from cell c.