Breach of contract

I have just got into contract with Telkom, received router a week ago but I am ****ed off already with the service. I was sold a contract of 9GB ********** per month. I phoned yesterday to enquire about the available data am left with, I was advised i have 9GB available. When I phoned in today, I was told I'm left with 200 MB, told the contract only offers 500mb not 9GB not as sold to me over the phone. This is a breach of contract and want Telkom to phone.