Highly unprofessional and poor service by Vodacom employees

So I decide to call vodacom this morning to cancel the extension of the contract I took a year ago after my first contract lapsed and the dom kop I spoke to tells me in order for the contract to cease I have to pay Vodacom R600 + when I ask him why so much he tells me it's 75% of the outstanding contract and that was explained to me when I extended the contract, and I tell him nothing like that was said and he says I read the contract which is something I also never received from them.