Unfair account

I was on a corporate account until 31.5.2018 under spend manager. From 1 June 2018 the account has been transferred to my own account. Everything used for May is for the corporate accountToday 8 June 2018 I received and email with the May account that will be deducted from my account on 30.6.2018 I phoned Vodacom and spoke to Pam and Ayanda and they told me that Im liable for the account of May and I have to claim it back if I feel they have to pay it. There is no way that a Government Dept will pay me back. Vodacom was suppose to send this account to the Dept and they have to fit the bill for May and not me. I feel that I am unfair billed for this account. I will pay what is due by my for June BUT not May. This is now a good time for me then to move my account to another service provider if this is the service that I received. Im with Vodacom for 20 years and the service just get worst