Trying to cancel contract proves to be impossible

I have been calling since 15 May 2015 to cancel my contract. The first time I called I was told it would incur charges and therefore I should wait until the Monday to cancel and was offered a different kind of contract and the man I had spoken to said he would call me on the Monday. On Monday I did not receive a call. I then called again during the week and was put through to the sales department and told the call centre is on strike. I then kept trying every week with no luck. Now I received the monthly airtime package and will be paying more since tariffs were increased. I called again yesterday and still no response. Why should customers suffer, if there is industrial action measures should be in place to ensure services continue. I want to cancel the contract which I faithfully paid for two years. Assistance will be highly appreciated.