Cancellation of my cell nr

I just contacted Vodacom to give notice for cancellation on my cell phone nr ***. The end date for this contract is 4 June 2015. The lady told me that I will be billed in full for June 2015 - which is not right, because I am already not using this cell nr. Please, can you clear this up with me - you are only allowed to bill until 4 June 2015. I contacted the ombudsman for communications and they say I am correct.<br> Otherwise, please cancel my account on 31 May. I have had it with Vodacom's bad service!