Nonsense service

I canceled my contract with Vodacom because I wasn't interested in upgrading. They said the contract would end on the last day of May. Haven't been using the sim card and there's a proration charge of something and I know that I didn't subscribe to anything. Whatever that they chose for me just so they can keep receiving money from me they must cancel it because I will not pay for any service that I didn't opt for just because a company I'd greedy