Contracts

So I just got a message from Edgars that my 6 months free plan is no longer available, does this mean that my original contract is now null and void, this is what I originally signed for and now they are breaking the contract, so in retrospect I don’t have to pay my remaining balance, last time I checked, South Africa still have laws where you are not allowed to just change a contract, if that is the case, why do I still have a cellphone contract.... If this is fact then I will not be paying my remaining balance and Edgars can go and do what they do best, fail.