Vodacom Negligence

I have an account with Vodacom (Contracts) I have 2 phones and a Laptop. I finished paying off the laptop in August 2017. My September 2017 bill came shooting sky high and I called the customer care to ask why, they told me that I recently upgrade with an iPhone. I then took all necessary steps to prove that I did not upgrade, they told me it was delivered to Soweto (Gauteng) and I live in Durban. They told me that they will hand the matter over to the investigating department. Even now in January 2018 nothing has been done about my case and my account is showing outstanding payment. My contracts are deactivated currently and no one is contacting me about this, when I call I get disconnected when am being transferred to investigation department.